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Shari'a and thesis statements for controversial issues Violence in essays of christmas, American Mosques. by Mordechai Kedar and David Yerushalmi. Middle East Quarterly. How great is the thesis statements for controversial issues, danger of extremist violence in the name of Islam in the United States? Recent congressional hearings into essays this question by Rep.
Peter King (Republican of New York), chairman of the thesis statements for controversial, Committee on on summer 7 Homeland Security, have generated a firestorm of statements issues, controversy among his colleagues, the press, and the general public. Though similar hearings have taken place at least fourteen times since 2001, King was labeled a latter-day Joe McCarthy and the hearings called an assault on civil liberties and a contemporary witch-hunt. Yet the larger dilemmas outlined by both the congressman and some of his witnesses remain: To what extent are American Muslims, native-born as well as naturalized, being radicalized by Islamists? And what steps can those who are sworn to of christmas, the protection of American citizenry take that will uncover and disrupt the plots of thesis statements for controversial, those willing to on summer 7, take up arms against others for statements the sake of jihad? Root Causes and Enabling Mechanisms. A comprehensive study of the relationship between Shari'a adherence and incitement to violence in American mosques found that mosques that segregated men from women during prayer service were more likely to contain violence-positive materials than those where men and women were not segregated. One study by Quintan Wiktorowicz, assistant professor of international studies at Rhodes College and now on the staff of the National Security Council, noted that modern jihadists legitimize their violent activities by relying on the same textual works as their nonviolent Salafist counterparts. However, the approach taken to these texts by the violent jihadist may be distinguished from that of the nonviolent Salafist insofar as the jihadist uses the principles advanced by article both classical and modern Islamic scholars and ideologues and adapts them to thesis for controversial, modern situations in a way that provides a broader sanction for the permissible use of violence.
Further, in 2007, Paul Gill concluded that terrorist organizations seek societal support by write unit creating a culture of martyrdom and that one theme common to suicide bombers was the support they received from a community that esteemed the thesis for controversial, concept of martyrdom. Thesis On Child Rights? Thus, a complex dynamic is at work between a terrorist organization, society, and individuals with the interplay between these three dimensions enabling radicalization and thesis for controversial terrorist attacks. Another item that may help to understand the growth of modern jihadism appears in Marc Sageman's 2004 study, which found that 97 percent of jihadists studied had become increasingly devoted to forms of essays critiquing, Salafist Islam highly adherent to Shari'a (Islamic law) while on their path to radicalization, despite many coming from less rigorous devotional levels during their youths. Statements For Controversial Issues? This increase in devotion to Salafist Islam was measured by outwardly observable behaviors such as wearing traditional Arabic, Pakistani, or Afghan clothing or growing a beard. When viewed together, a picture emerges that may give researchers, as well as law enforcement officials, a way to monitor or potentially to predict where violent jihad may take root. Potential recruits who are swept up in this movement may find their inspiration and how to encouragement in a place with ready access to classic and modern literature that is statements for controversial, positive toward jihad and violence, where highly Shari'a-adherent behavior is practiced, and where a society exists that in some form promotes a culture of essay on summer vacation for class 7, martyrdom or at statements least engages in on summer vacation for class 7, activities that are supportive of violent jihad. The mosque can be such a place. That the thesis for controversial issues, mosque is a societal apparatus that might serve as a support mechanism for thesis in india violent jihad may seem self-evident, but for it to statements, be a useful means for thesis on child in india measuring radicalization requires empirical evidence. A 2007 study by the New York city police department noted that, in the context of the thesis issues, mosque, high levels of Shari'a adherence, termed Salafi ideology by the authors of the report, may relate to scholarship without, support for thesis for controversial violent jihad. Specifically, it found that highly Shari'a-adherent mosques have played a prominent role in radicalization. Another study found a relationship between frequency of mosque attendance and a predilection for supporting suicide attacks but discovered no empirical evidence linking support for suicide bombings to some measure of religious devotion (defined and essays of christmas measured by frequency of prayer).
However, the thesis statements issues, study suffers from a major methodological flaw, namely, reliance on self- reporting of copy, prayer frequency. Muslims would be under social and thesis psychological pressure to report greater prayer frequency because their status as good or pious believers is linked to whether they fulfill the religious obligation to article, pray five times a day. This piety is statements for controversial, not dependent on regular mosque attendance as Muslims are permitted to essays of christmas, pray outside of statements for controversial, a mosque environment whenever necessary. Hence, the pressure to over-report exists for self-reporting of prayer frequency but is not present in self-reporting of frequency of mosque attendance, which is essay vacation, a measure of thesis, both coalitional or group commitment and religious devotion. Thus, there is essays of christmas, a need for the study and corroboration of a relationship between high levels of Shari'a adherence as a form of religious devotion and coalitional commitment, Islamic literature that shows violence in a positive light, and institutional support for violent jihad. By way of filling this lacuna, the authors of this article undertook a survey specifically designed to determine empirically whether a correlation exists between observable measures of thesis statements, religious devotion linked to Shari'a adherence in American mosques and on summer vacation the presence of violence-positive materials at those mosques. The survey also sought to for controversial issues, ascertain whether a correlation exists between the presence of violence-positive materials at a mosque and of christmas the promotion of jihadism by the mosque's leadership through recommending the study of these materials or other manifest behaviors.
Identifying Shari'a-Adherent Behaviors. Shari'a is the Islamic system of thesis for controversial issues, law based primarily on two sources held by Muslims to be respectively direct revelation from God and divinely inspired: the Qur'an and the Sunna (sayings, actions, and traditions of Muhammad). There are other jurisprudential sources for critiquing article Shari'a derived from the legal rulings of Islamic scholars. These scholars, in turn, may be adherents of differing schools of Islamic jurisprudence. Notwithstanding those differences, the divergence at the level of for controversial, actual law is, given the fullness of the corpus juris, confined to relatively few marginal issues.
Thus, there is general unity and agreement across the Sunni-Shiite divide and across the various Sunni madh'habs (jurisprudential schools) on core normative behaviors. Surveyors were asked to how to write, observe and record selected behaviors deemed to for controversial, be Shari'a-adherent. These behaviors were selected precisely because they constitute observable and measurable practices of an orthodox form of Islam as opposed to internalized, non-observable articles of faith. Such visible modes of conduct are considered by traditionalists to thesis, have been either exhibited or commanded by Muhammad as recorded in the Sunna and later discussed and preserved in canonical Shari'a literature. The selected behaviors are among the most broadly accepted by legal practitioners of Islam and are not those practiced only by a rigid subgroup within Islam—Salafists, for statements issues example.
Among the behaviors observed at rights the mosques and scored as Shari'a-adherent were: (a) women wearing the hijab (head covering) or niqab (full-length shift covering the entire female form except for the eyes); (b) gender segregation during mosque prayers; and (c) enforcement of straight prayer lines. Behaviors that were not scored as Shari'a-adherent included: (a) women wearing just a modern hijab , a scarf-like covering that does not cover all of the thesis for controversial issues, hair, or no covering; (b) men and essays women praying together in statements issues, the same room; and (c) no enforcement by the imam, lay leader, or worshipers of straight prayer lines. The normative importance of a woman's hair covering is evidenced by two central texts, discussed at length below, Reliance of the Traveller and without Fiqh as-Sunna (Law of the Sunna), both of which express agreement on the obligation of a woman to wear the hijab : There is no such dispute over thesis what constitutes a woman's aurah [private parts/nakedness]. It is stated that her entire body is aurah and must be covered, except her hands and face … God does not accept the prayer of an adult woman unless she is wearing a head covering ( khimar , hijab ). The nakedness of a woman (even if a young girl) consists of the whole body except the article, face and hands. The nakedness of a woman is that which invalidates the prayer if exposed. … It is recommended for a woman to wear a covering over her head ( khimar ), a full length shift, and statements issues a heavy slip under it that does not cling to the body. In a similar fashion, Shari'a requires that the genders be separated during prayers. While both Reliance of the Traveller and Fiqh as-Sunna express a preference that women should pray at home rather than the mosque, they agree that if women do pray in the mosque, they should pray in without, lines separate from the men. Additionally, authoritative Shari'a literature agrees that the men's prayer lines should be straight, that men should be close together within those lines, and that the thesis, imam should enforce prayer line alignment. The mosques surveyed contained a variety of texts, ranging from contemporary printed pamphlets and for class handouts to classic texts of the Islamic canon.
From the thesis for controversial, perspective of promoting violent jihad, the literature types were ranked in the survey from essay 7, severe to moderate to thesis for controversial issues, nonexistent. The texts selected were all written to serve as normative and instructive tracts and are not scriptural. This is important because a believer is free to understand scripture literally, figuratively, or merely poetically when it does not have a normative or legal gloss provided by Islamic jurisprudence. The moderate-rated literature was authored by respected Shari'a religious and/or legal authorities; while expressing positive attitudes toward violence, it was predominantly concerned with the thesis rights, more mundane aspects of religious worship and thesis for controversial issues ritual. The severe material, by contrast, largely consists of relatively recent texts written by ideologues, rather than Shari'a scholars, such as Abul Ala Mawdudi and Sayyid Qutb. These, as well as materials published and disseminated by the Islamist Muslim Brotherhood, are primarily, if not exclusively, aimed at using Islam to advance a violent political agenda. Mawdudi (1903-79), for essays of christmas one, believed that it was legitimate to wage violent jihad against infidel colonizers in order to gain independence and for controversial spread Islam. His Jihad in Islam , found in many of the mosques surveyed, instructed followers to employ force in pursuit of a Shari'a-based order:
These [Muslim] men who propagate religion are not mere preachers or missionaries, but the functionaries of God [so that they may be witnesses for the people], and it is their duty to how to unit, wipe out thesis statements for controversial issues oppression, mischief, strife, immorality, high handedness, and unlawful exploitation from the world by force of arms. Similarly, Qutb's Milestones serves as the political and ideological backbone of the current global jihad movement. Qutb, for example, sanctions violence against those who stand in the way of how to, Islam's expansion: If someone does this [prevents others from accepting Islam], then it is the duty of Islam to fight him until either he is killed or until he declares his submission. These materials differ from other severe- and statements issues moderate-rated materials because they are not Islamic legal texts per se but rather are polemical works seeking to advance a politicized Islam through violence, if necessary. Nor are these authors recognized Shari'a scholars. The same cannot be said for some classical works that are also supportive of how to, violence in the name of Islam. Works by several respected jurists and scholars from the for controversial, four major Sunni schools of jurisprudence, dating from the how to write unit, eighth to fourteenth centuries, are all in agreement that violent jihad against non-Muslims is a religious obligation. Such behavior is normative, legally-sanctioned violence not confined to modern writers with a political axe to grind.
Nor does its presence in classical Muslim works make it a relic of some medieval past. Thesis Statements For Controversial Issues? While Umdat as-Salik (Reliance of the Traveler) may have been compiled in the fourteenth century, al-Azhar University, perhaps the preeminent center of Sunni learning in the world, stated in how to write, its 1991 certification of the English translation that the book conforms to the practice and faith of the orthodox Sunni community. While addressing a host of theological matters and thesis statements for controversial detailed instructions as to how Muslims should order their daily routine to demonstrate piety and application without essays commitment to thesis for controversial, Islam, this certified, authoritative text spends eleven pages expounding on the applicability of on summer 7, jihad as violence directed against non-Muslims, stating for for controversial issues example: The caliph … makes war upon write unit Jews, Christians, and Zoroastrians … provided he has first invited them to enter Islam in faith and practice, and if they will not, then invited them to enter the social order of Islam by paying the non-Muslim poll tax. The caliph fights all other peoples until they become Muslim … because they are not a people with a book, nor honored as such, and are not permitted to thesis statements for controversial issues, settle with paying the poll tax. The Fiqh as-Sunna and Tafsir Ibn Kathir are examples of works that were rated moderate for purposes of this survey. The former, which focuses primarily on the internal Muslim community, the family, and the individual believer and not on violent jihad, was especially moderate in its endorsement of application without, violence. Relatively speaking, the Fiqh as-Sunna expresses a more restrained view of violent jihad, in that it does not explicitly call for for controversial issues a holy war against essays the West even though it understands the Western influence on Islamic governments as a force that is destructive to Islam itself. Nonetheless, such texts do express positive views toward the use of violence against the other, as expressed in the following: Ibn Abbas reported that the Prophet, upon whom be peace, said, The ties of Islam and the principles of the statements for controversial issues, religion are three, and whoever leaves one of them becomes an essays unbeliever, and his blood becomes lawful: testifying that there is no god except God, the obligatory prayers, and the fast of Ramadan. Statements For Controversial Issues? … Another narration states, If anyone leaves one of [the three principles], by God he becomes an essays of christmas unbeliever, and no voluntary deeds or recompense will be accepted from statements, him, and his blood and wealth become lawful. Essays Critiquing? This is a clear indication that such a person is to thesis issues, be killed. Similarly in Tafsir Ibn Kathir : Perform jihad against the disbelievers with the sword, and be harsh with the hypocrites with words, and this is the jihad performed against them.
The survey's findings, explored in depth below, were that 51 percent of mosques had texts that either advocated the use of violence in the pursuit of a Shari'a-based political order or advocated violent jihad as a duty that should be of paramount importance to a Muslim; 30 percent had only texts that were moderately supportive of violence like the Tafsir Ibn Kathir and Fiqh as-Sunna ; 19 percent had no violent texts at all. A representative sample of one hundred mosques throughout the United States was surveyed. Essay On Summer For Class? Table 1 presents the distribution of mosques by thesis for controversial issues state. Write Unit? One quarter of the mosques had 10 or fewer worshipers; 50 percent had up to 28 worshipers; 75 percent had up to 70; the largest mosque had an estimated 1,700 worshipers. Table 1: Number of Mosques Surveyed by State. The study found a statistically significant association between the severity of violence-positive texts on statements for controversial issues mosque premises and Shari'a-adherent behaviors. As indicated in Table 2, mosques that segregated men from essay on summer, women during prayer service were more likely to contain violence-positive materials than those mosques where men and women were not segregated. Mosques that did not segregate genders were also less likely to thesis, possess violence-positive materials (26 percent) but nonetheless did carry both moderate (27 percent) and severe materials (47 percent). Table 2: Shari'a-adherent Mosques and Violence-positive Materials. Segregation in prayer.
Imam or lay leader has Sunna beard. [ii] Has Riyadh as-Salaheen (n=7) or more extreme fiqh material. [iii] In 1 mosque there was no prayer and surveyor could not determine the without, usual practice. [iv] 4 mosques did not have a leader. [v] 3 with no beard included in this category. [vi] 3 had traditional beards with henna; and all were in the severe group. Statements? They were combined with this group for rights ease of reporting.
[vii] In 1 case it was not determined. As was the case with gender segregation, those mosques that displayed strict alignment of statements for controversial issues, men's prayer lines were more likely than their less observant counterparts to contain materials from both the moderate and severe categories. Thus, 59 percent of of christmas, such mosques contained severe texts as opposed to 42 percent of mosques that did not enforce strict prayer line alignment. Conversely, only 4 percent of mosques with strict prayer line alignment possessed no violence-positive texts while 36 percent of statements for controversial issues, their less observant counterparts exhibited no such literature. Whether the mosque's imam or lay leader wore a traditional beard was also predictive of whether the mosque would contain violence-positive materials on premises. Essays Critiquing? Of the mosques led by traditionally bearded imams, 61 percent contained literature in the severe category, 33 percent contained only moderate-rated materials, and for controversial issues 7 percent did not contain any. Forty-six percent of the mosques in which the imam did not wear a traditional beard contained severe materials, 28 percent had moderate-rated texts, and 26 percent contained none on of christmas site. Other aspects of an imam's or lay leader's appearance, such as wearing a head covering or traditional garb like a thoub (full-length, white gown with long sleeves) were not statistically significant. Table 3 reveals another statistically significant finding associated with mosque attendance. Mosques that contained written materials in the severe category were the best attended, followed by those with only moderate-rated materials, trailed in turn by thesis statements those lacking such texts.
Mosques with severe materials had a mean attendance of essays, 118 worshipers while mosques containing only moderate materials had a mean attendance of issues, 60 worshipers; mosques that contained no violence-positive literature had a mean attendance of 15 worshipers. Table 3: Violence-positive Materials, Mosque Attendance, and essay vacation for class 7 Shari'a-based Worshiper Characteristics. [ii] Has Riyadh as-Salaheen (n=7) or more extreme fiqh material. [iii] In 2 mosques only the imam was present. [iv] Data in parentheses that follow percentage figures denote the standard deviation. [v] Women were present in 65 mosques. [vi] Boys were present in 63 mosques. The adoption or rejection of Western dress by male worshipers was yet another telling indicator of the thesis, presence of violence-positive materials.
In mosques that contained no violence-positive materials, an average of 73 percent of the copy essay without, men wore Western garb. In those mosques in which only moderate literature was available, 35 percent of male worshipers wore Western clothing; almost the same figure (34 percent) was exhibited in mosques featuring Qutb, et al. The survey was unable to find a statistically significant indicator when it came to women wearing a modern hijab as opposed to the more conservative traditional hijab , which covers all of the hair, or the niqab , which covers the thesis for controversial issues, whole body other than the eyes. This category recorded the distinction between an adult female worshiper wearing the less conservative modern hijab and the traditional Shari'a-adherent hijab and niqab . Perhaps more troubling than the correlation between jihadist literature and Shari'a-adherent behaviors within a mosque was the role played by imams in recommending that worshipers study material that promote violence. The more manifestly Shari'a-adherent a mosque, the more likely its imam was to recommend the study of violence-positive texts. Thus, as seen in Table 4, 96 percent of the imams in mosques that observed strict prayer line alignment recommended such reading material. Copy Essay? Similarly, 93 percent of the for controversial issues, imams who sported a traditional, full beard endorsed the study of such writings.
But while the presence of certain Shari'a-adherent behaviors correlated almost one-to-one with the promotion of the violence-positive texts, the absence of these attributes should not be construed as a sign of essays, true moderation. In mosques that did not practice strict prayer line alignment, a striking 72 percent of imams nonetheless recommended violence-positive materials. Similarly, 78 percent of imams who did not wear a traditional beard were proponents of these texts. Table 4: Shari'a-based Mosque Prayer, Shari'a-based Imam Characteristics, and Imam Recommended Violence-positive Material. Segregation in prayer. Beard of imam or lay leader. [ii] In 4 mosques, neither an imam nor a lay leader was present. Issues? However, in 1 of critiquing, these 4 cases the imam had made clear recommendations on the mosque's webpage. [iii] In 1 case it was not determined. Moreover, mosques where the imam recommended violence-positive materials for study were marked by a higher presence of for controversial, worshipers—both men and women—who took on how to write unit a Shari'a-adherent appearance and a lower percentage of worshipers of a more assimilative or Western appearance (see Table 5).
As such, these mosques were much better attended than those where such materials were not promoted. Imams at 82 of the thesis issues, 100 mosques surveyed recommended that worshipers study violence-positive materials; these mosques experienced a mean attendance of 96 worshipers and for class 7 a median attendance of 39. At the thesis, same time, at the 15 mosques surveyed where the essays, imam did not recommend the study of such texts, the mean attendance was approximately 17 worshipers with a median attendance figure of 4. Table 5: Mosque Attendance, Shari'a-based Worshiper Characteristics, and Imam Recommended Violence-positive Material. [ii] Data in parentheses that follow percentage figures denote the statements for controversial issues, standard deviation. [iii] Women were present in 65 mosques. Data collected on percent women with niqab (rare), hijab, and modern hijab. The survey found a strong correlation between the presence of severe violence-promoting literature and mosques featuring written, audio, and video materials that actually promoted such acts. By promotion of thesis in india, jihad, the study included literature encouraging worshipers to engage in terrorist activity, to provide financial support to for controversial issues, jihadists, and to essay without, promote the establishment of a caliphate in the United States. These materials also explicitly praised acts of terror against for controversial the West; praised symbols or role models of violent jihad; promoted the use of force, terror, war, and violence to implement the scholarship without essays, Shari'a; emphasized the inferiority of non-Muslim life; promoted hatred and intolerance toward non-Muslims or notional Muslims; and endorsed inflammatory materials with anti-U.S. Thesis For Controversial Issues? views.
As Table 6 demonstrates, of the 51 mosques that contained severe materials, 100 percent were led by imams who recommended that worshipers study texts that promote violence. Table 6: Violence-positive Materials and without Promotion of Violent Jihad. [ii] Has Riyadh as-Salaheen (n=7) or more extreme fiqh material. [iii] Denominator is 17, 2 in this column had no imam or leader. For example, mosques containing violence-positive materials were substantially more likely to thesis statements for controversial, include materials promoting financial support of terror than mosques that did not contain such texts. A disturbing 98 percent of mosques with severe texts included materials promoting financial support of terror. Those with only moderate-rated materials on site were not markedly different, with 97 percent providing such materials. These results stand in stark contrast to the mosques with no violence-positive materials on copy their premises where only 5 percent provided materials urging financial support of terror. These results were comparable when using other indicators of jihad promotion. Thus, 98 percent of mosques that contained severe-rated literature included materials promoting establishing an Islamic caliphate in the United States as did 97 percent of mosques containing only moderate-rated materials.
By contrast, only one out thesis statements for controversial issues of the 19 mosques (5 percent) that had no violence-positive literature advocated this. Similarly, mosques with severe or moderate materials invited speakers known to have promoted violent jihad (76 percent and 60 percent respectively) versus one mosque out of how to write unit, 19 (5 percent) which did not contain violence-positive texts. Finally, three patterns of behavior indicating promotion of violent jihad did not strongly correlate to the presence of violence-positive literature. Despite the thesis for controversial issues, presence of severe texts in such mosques, only a small number actually encouraged joining a terrorist organization, openly collected monies for such organizations, or distributed memorabilia featuring jihadists or terrorist organizations. Write Unit? Although very few mosques engaged openly in these activities, a correlation between these activities and the presence and severity of violence-positive literature was shown to exist. The conclusions to be drawn from thesis statements issues, this survey are dismal at scholarship without essays best, offering empirical support for previous anecdotal studies on the connection between highly Shari'a-adherent mosques and political violence in the name of Islam.
The mosques where there were greater indicators of Shari'a adherence were more likely to contain materials that conveyed a positive attitude toward employing violent jihad against the West and non-Muslims. The fact that spiritual sanctioners who help individuals become progressively more radicalized are connected to highly Shari'a-adherent mosques is for controversial issues, another cause for deep concern. In almost every instance, the imams at the mosques where violence-positive materials were available recommended that worshipers study texts that promoted violence. The survey also demonstrates that there are mosques and mosque-going Muslims who are interested in thesis rights in india, a non-Shari'a-centric Islam where tolerance of the other, at least as evidenced by the absence of jihad-promoting literature, is the norm. Mosques where violence-positive literature was not present exhibited significantly fewer indicators of orthodox, Shari'a-adherent behaviors and were also significantly less likely to thesis, promote violent jihad or invite speakers supportive of violent jihad. These non-Shari'a-centric mosques may provide a foundation from without, which a reformed Islam and statements its followers can more completely integrate into liberal, Western citizenship. The results of essays article, this survey do not indicate the percentage of American Muslims that actually attend mosques with any regularity, nor does it reveal what relative percentage of American Muslims demonstrate Shari'a-adherent or non-adherent behaviors. Thesis Statements For Controversial? Moreover, although this study shows that imams at Shari'a-adherent mosques recommend studying violence-positive materials and thesis on child rights utilize their mosques for thesis issues support of violent jihad, it does not capture the individual attendees' attitudes toward religiously sanctioned violence. However, it is at least reasonable to conclude that worshipers at such mosques are more sympathetic to the message of the literature present at those mosques and to what is essay on summer vacation, being preached there. A follow-up survey of individual mosque attendees would provide insight regarding the thesis for controversial issues, relationship, if any, between Shari'a-adherence on the individual level and the individual's attitude toward violent jihad. A recent study by Andrew F. How To Unit? March examined whether Islamic doctrine would allow Muslims to cooperate socially with non-Muslims and thesis statements issues sincerely affirm liberal citizenship as that term is understood in its Western, democratic sense. He argued that there were grounds for an overlapping consensus but also noted that present-day Salafists cite texts holding that Muslims are either at war with non-Muslims or, at best, are in a state devoid of any obligation to cooperate socially with them. Additionally, March noted that the underpinnings of his theoretical consensus might be negated by how to write unit empirical evidence showing that a large percentage of Muslims are unaware of [or reject] arguments that advocate for Western notions of liberal citizenship.
Although released before March's study, an April 2007 survey conducted by issues WorldPublicOpinion.org presented such empirical evidence. The survey found that majorities in Morocco, Egypt, Pakistan, and Indonesia—ostensibly moderate Muslim countries—favored a strict application of without, Shari'a law in every Islamic country and keeping Western values out of Islamic counties. However, that survey reports the attitudes of residents in non-Western countries that enforce Shari'a to varying degrees. It might be expected that Muslims in the West—who are immersed in Western culture, values, and democracy—would express different attitudes than their counterparts in the Middle East, Far East, and North Africa. Unfortunately, the results of the thesis statements, current survey strongly suggest that Islam—as it is generally practiced in vacation 7, mosques across the United States—continues to manifest a resistance to the kind of tolerant religious and statements issues legal framework that would allow its followers to make a sincere affirmation of liberal citizenship. This survey provides empirical support for essays critiquing article the view that mosques across America, as institutional and social settings for mosque-going Muslims, are at least resistant to social cooperation with non-Muslims.
Indeed, the statements issues, overwhelming majority of mosques surveyed promoted literature supportive of how to write, violent jihad and a significant number invited speakers known to have promoted violent jihad and other behaviors that are inconsistent with a reasonable construct of liberal citizenship. This survey suggests that, first and foremost, Muslim community leaders must take a more active role in educating their own faith community about the dangers associated with providing a safe haven for violent literature and its promotion—whether that safe haven is the mosque or the social club. These results also suggest that researchers and counterterrorist specialists should pay closer attention to the use and exploitation of classic Islamic legal doctrine and jurisprudence for recruiting and generating a commitment to violence against for controversial the perceived enemies of Islam. Finally, these findings should engender at least an interest among researchers to essays of christmas, begin to study carefully Muslim attitudes toward citizenship and violence but one that differentiates between those who are Shari'a-adherent and those who are not. And, among Shari'a adherents, this future survey data must be sensitive to the distinction between traditionalism, orthodoxy, and Salafism, along with the more obvious sect distinctions, such as between Sunnis and thesis statements for controversial Shiites. Non-Shari'a-adherent communal prayer occurs when men and women are not segregated during the prayer service and the genders mix. Non-Shari'a-adherent alignment of men's prayer lines occurs when there is no observable attention paid to strict alignment of the unit, men's prayer lines. A non-Sunna style beard is either limited to a chin-beard or if the imam or lay leader wears no beard at all. Non-Shari'a adherent behavior is that the for controversial, imam or lay leader did not wear a religious head covering.
Non-Shari'a-adherent garb is thesis rights in india, Western-style clothing such as modern-style dress or casual pants and shirt. Wearing the watch on the left wrist or not wearing a watch at all. Non-Shari'a-adherent behavior is for an adult male worshiper to have no beard. Non-Shari'a-adherent behavior is for an adult male to not wear a religious hat. Non-Shari'a-adherent behavior is to wear Western-style clothing such as pants not rolled up above the ankles.
Non-Shari'a-adherent behavior is to wear the modern hijab (a scarf that does not completely cover the hair) or to not wear any hair covering. Non-Shari'a-adherent behavior is to thesis for controversial issues, not wear the hijab. Non-Shari'a-adherent behavior is to not wear a religious head covering. If the critiquing, surveyor found the Riyadh as-Salaheen , works by statements for controversial Qutb or Mawdudi, or similar materials, then the mosque was categorized as containing severe-rated materials. If the surveyor found no violence-positive materials or if the violence-positive materials constituted less than 10% of all available materials, then the copy essay, mosque was categorized as containing no materials. If the imam or lay leader recommended studying any of the issues, materials mentioned above except the Qur'an and/or Sunna, then the imam or lay leader was recorded as having recommended the study of texts promoting the rated material.  According to Islamic jurisprudence, Shari'a adherence can be measured across several normative axes, such as obligatory-prohibited, recommended-discouraged, and simply permissible.
In theory, every act of a Shari'a-adherent Muslim falls within one of the normative categories—that is, there is no behavior outside of Shari'a. For purposes of this survey, the authors have chosen, except where indicated by notation, the obligatory-prohibited and without the recommended-discouraged or recommended-permissible axes, which we have demarcated Shari'a-adherent/non- Shari'a-adherent, respectively.  If a mosque, on thesis statements for controversial issues the basis of materials observed by for class 7 the surveyor, was recorded as having: (a) promoted violent jihad; (b) promoted joining a terrorist organization; (c) promoted financial support of terror; (d) collected money openly at for controversial the mosque for a known terrorist organization; (e) promoted establishing the Caliphate in the U.S.; (f) praised terror against the West; (g) distributed memorabilia featuring jihadists or terrorist organizations; or (h) invited imams or preachers who are known to have promoted violent jihad, then the materials that the surveyor relied on thesis to record the presence of this material were subject to a secondary review by a committee of thesis statements for controversial issues, three subject-matter experts. Essay Vacation For Class? This secondary review was collected and reviewed by the experts evaluating the materials independently of one another. A consensus view of two of the three experts was required to confirm the surveyor's observation. In 63 percent of the cases, the materials were so explicit in their promotion, praise, or support for the above behaviors that the committee's decision was unanimous. In no instance was there not a consensus and agreement with the surveyor's observation.  The different legal schools vary on whether a beard is statements for controversial issues, obligatory or preferable; they also differ on whether the beard for thesis on child rights purposes of fiqh is only the chin hairs or also the lateral hairs of the sideburns and cheeks; and they differ on the minimum required length before trimming is permitted.
The majority view, taking into account all schools and thesis statements the Salafist opinions, is that a full beard is Sunna (following the behavior of Muhammad) and essays critiquing if not obligatory, preferable. For purposes of thesis, this survey, the copy, full beard, trimmed or not, was considered Shari'a-adherent and for controversial issues a chin beard or no beard, was considered as non-Sunna, and in rights in india, the survey's lexicon, non-adherent.  While wearing a watch on the right hand is not strictly speaking a Shari'a requirement, during the preparation of the methodology of this survey, the authors identified literature at several mosques attended by Salafists advocating the wearing of a watch on the right hand for two reasons: not to wear jewelry on the left hand to follow the mode of dress of Muhammad, who, based upon certain Sunna, did not wear jewelry on his left hand; and to for controversial issues, avoid dressing in essays critiquing, the way of non-Muslims. The authors decided to add this observation to determine whether this behavior translated into for controversial issues observance by the more fundamentalist Salafists. Thesis? They also observed that the 12 imams who wore the watch on the right hand were right handed.  All of the materials characterized from thesis statements for controversial, this point to the end of the survey were dated or produced prior to September 11, 2001 but were still available or sold by the mosque in prominent fashion. Sampling: The survey analyzed data collected from a random sample of 100 mosques. Essays Critiquing? This sample size provided sufficient statistical power to find a statistically significant association between most of the selected Shari'a-adherent behaviors and violence-positive variables. Most Shari'a adherence and statements for controversial issues violence-positive variables exhibited a strong correlation while some exhibited a weak or no correlation.
A sample size of 100 mosques also allowed the copy essay, survey to extrapolate to all mosques in the United States at a 95 percent confidence interval with a margin of error of +/-9.6 percent. The survey was developed by using state-by-state estimates of the Muslim population extracted from the only extant such survey. This was then used to create a listing of thesis statements issues, all states whose Muslim population represented at least 1 percent of the estimated total United States Muslim population. Fourteen states and the District of Columbia (15 randomly selected states) were randomly selected from the final listing to accommodate limits on physical logistics and personnel resources for the actual survey. For each of the fourteen states and D.C., cities with the highest estimated concentrations of on child rights in india, Muslims were identified, and mosques within those areas were eventually selected. The survey combined the data on 1,209 mosques listed in The Mosque in America: A National Portrait with the data on the 1,659 mosques obtained online from statements for controversial issues, Harvard's Pluralism Project, with duplicates eliminated. Mosques were excluded from the list if there were indications that they were no longer operating, with a final site list yielding a total of 1,401 potential mosques for essays the survey. The dates and prayer times for visiting mosques were also randomly selected. If a mosque was found to be closed, abandoned, or not at thesis statements issues the address listed, then the next mosque that appeared on the randomized list for that city was visited.
When the essays, dominant language of the subject mosque was determined to be other than English, such as Arabic, Urdu, or Farsi, the surveyor who visited the statements for controversial, mosque was fluent in that language. Each mosque was visited twice, once between May 18, 2007, and without December 4, 2008 (Survey Period), and then again between May 10, 2009, and May 30, 2010 (Audit Period). The results of the Audit Period confirmed the findings in the Survey Period in all but nine mosques. Data Collection: A surveyor visited a subject mosque in thesis, order: (a) to observe and record 12 Shari'a-adherent behaviors of the worshipers and the imam (or lay leader); (b) to observe whether the mosque contained the selected materials rated as moderate and without severe; (c) to observe whether the mosque contained materials promoting, praising, or supporting violence or violent jihad; and (d) to observe whether the statements, mosque contained materials indicating the mosque had invited guest speakers known to have promoted violent jihad. Thesis On Child Rights In India? (See Appendix A for thesis issues a more detailed presentation of the essays critiquing article, survey variables and for controversial methodology.) Thus, the survey only examined the presence of Shari'a-adherent behaviors, the presence of essay on summer vacation for class 7, violence-positive materials in mosques, whether an imam would promote the study of violence-positive materials, and whether a mosque was used as a forum to statements for controversial, promote violent jihad. Copy Without? Since there is no central body to which all mosques belong, it was difficult to ascertain that the sampling universe list was complete. Issues? This may have introduced bias into the sampling although the authors find no evidence of any systemic distortions. Mordechai Kedar is an assistant professor in critiquing article, the departments of Arabic and Middle East studies and statements a research associate with the Begin-Sadat (BESA) Center for application without Strategic Studies, both at Bar Ilan University, Israel. David Yerushalmi is general counsel for The Center for Security Policy in Washington, D.C., and thesis statements issues director of policy studies at the Institute for Advanced Strategic and Political Studies in Potomac, Md.  Timeline of the essay on summer for class, Committee's Work on Violent Islamist Radicalization, Senate Committee on Homeland Security and for controversial Governmental Affairs, Washington, D.C., accessed Mar.
24, 2011.  Morning Edition , National Public Radio, Jan. 24, 2011.  Quintan Wiktorowicz, A Genealogy of Radical Islam, Studies in Conflict and Terrorism , 28 (2005), pp. 75-97.  See Paul Gill, A Multi-Dimensional Approach to Suicide Bombing, International Journal of Conflict and write Violence , 2 (2007), pp.
142-59.  Marc Sageman, Understanding Terror Networks (Philadelphia: University of statements, Pennsylvania Press, 2004), p. 93.  Mitchell D. Silber and essay without Arvin Bhatt, Radicalization in for controversial issues, the West: The Homegrown Threat (New York: New York City Police Department, 2007), pp. 2-90.  Jeremy Ginges, Ian Hansen, and essays article Ara Norenzayan, Religion and thesis issues Support for Suicide Attacks, Psychology Science , 2 (2009), pp. 224-30.  Saba Mahmood, Rehearsed Spontaneity and scholarship essays the Conventionality of Ritual: Disciplines of Salat, American Ethnologist , Nov.
2004, pp. 827-53.  Daniel Winchester, Embodying the Faith: Religious Practice and the Making of Muslim Moral Habitus, Social Forces , June 2008, pp. For Controversial? 1753-80; Sayyid Sabiq, Fiqh as-Sunna (Indianapolis: American Trust Publications, 1991), vol. 2, pp. How To Unit? 67-74.  Ahmad ibn Naqib al-Misri, Reliance of the Traveller and Tools for the Worshipper , trans.
Sheikh Nuh Ha Mim Keller, p. Thesis Statements? vii, accessed Nov. 21, 2010; Wael B. Hallaq, Shari'a: Theory, Practice, Transformations (Cambridge: Cambridge University Press, 2009), pp. 72-8, 113-24.  Sabiq, Fiqh as-Sunna , vol. 1, p. Of Christmas? 113.
 Ibid., F12.4; Sabiq, Fiqh as-Sunna , vol. 2, pp. 50, 56.  Sayyid Qutb, Milestones , in Studies in statements, Islam and the Middle East, 2005, p. 34.  Hallaq, Shari'a: Theory, Practice, Transformations , pp.
324-34; Majid Khadduri, War and Peace in the Law of Islam (Baltimore: Johns Hopkins University Press, 2008), pp. 42-137; Rudolph Peters, Jihad in Classical and Modern Islam , 2nd ed. (Princeton, N.J.: Markus Wiener Publications, 2005), pp. 1-57; David Cook, Understanding Jihad (Berkeley: University of California Press, 2005), pp. 13-92; Majid Khadduri, trans., The Islamic Law of Nations: Shaybani's Siyar (Baltimore: The Johns Hopkins Press, 1965), pp. Thesis On Child In India? 1-22; Mary Haybeck, Knowing the Enemy: Jihadist Ideology and the War on Terror (New Haven: Yale University Press, 2006), pp. 107-33; David Yerushalmi, Selected Classical Sources on Jihad, 2009, accessed Nov. 6, 2010.  Al-Azhar certification of Reliance of the Traveller , Islamic Research Academy, al-Azhar University, Cairo, Feb. 11, 1991.  Sabiq, Fiqh as-Sunna , vol. 3, p. 76.
 Hafiz Ibn Kathir, Tafsir Ibn Kathir (Houston: Darussalam Publishers, 2000), vol. Issues? 4, p. 475.  See, for example, The New York Daily News , Nov. 11, 2009.  Andrew F. Without? March, Islam and Liberal Citizenship: The Search for an Overlapping Consensus (New York: Oxford University Press, 2009), p. 266.  Muslim Public Opinion on U.S. Policy, Attacks on Civilians, and statements Al Qaeda, The Program on International Policy Attitudes at the University of scholarship without essays, Maryland, WorldPublicOpinion.org, Apr. 24, 2007.  Barry A. Kosmin and Seymour P. Lachman, One Nation under God: Religion in thesis statements for controversial issues, Contemporary American Society (New York: Harmony Books, 1993), pp. 96-7.
 Ihsan Bagby, Paul M. Perl, and essays critiquing Bryan T. Froehle, The Mosque in thesis statements issues, America: A National Portrait, Council on American Islamic Relations, Washington, D.C., Apr. 26, 2001.  Directory of Religious Centers, Pluralism Project, Harvard University, Cambridge, accessed Oct. 30, 2010. Related Topics: Islamic law (Shari'a), Muslims in the United States | Mordechai Kedar | Summer 2011 MEQ receive the latest by email: subscribe to vacation 7, the free mef mailing list This text may be reposted or forwarded so long as it is statements issues, presented as an integral whole with complete and accurate information provided about its author, date, place of publication, and original URL.
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cmu thesis database Java(TM) - see bottom of thesis statements, page. Our valued sponsors who help make this site possible. Note that this page is very large. The tips on this page are categorized in other pages.
Use the tips index page to access smaller focused listings of tips. This page lists many other pages available on the web, together with a condensed list of tuning tips that each page includes. For the without, most part I've eliminated any tips that are wrong, but one or two may have slipped past me. Remember that the statements issues, tuning tips listed are not necessarily good coding practice. They are performance optimizations that you probably should not use throughout your code. Instead they apply to speeding up critical sections of without essays, code where performance has already been identified as a problem. The tips here include only those that are available online for free. Statements Issues? I do not intend to summarize any offline resources (such as the copy essay without, various books available including mine, Java Performance Tuning). The tips here are of very variable quality and usefulness, some real gems but some dross and statements quite a bit of repetition. Comments in how to square brackets, , have been added by me.
Use this page by using your browser's find or search option to identify particular tips you are interested in on the page, and follow up by reading the issues, referenced web page if clarification is necessary. This page is currently 411KB. This page is updated once a month. You can receive email notification of any changes by subscribing to the newsletter. Performance planning for managers (Page last updated February 2001, Added 2001-03-21, Author Jack Shirazi, Publisher OnJava). Tips: Include budget for performance management. How To Unit? Create internal performance experts. Set performance requirements in the specifications.
Include a performance focus in the analysis. Require performance predictions from the design. Create a performance test environment. Test a simulation or skeleton system for validation. Integrate performance logging into the application layer boundaries. Performance test the system at multiple scales and tune using the resulting information Deploy the system with performance logging features. A long list of most of the tuning techniques covered in my Java Performance Tuning book (Page last updated August 2000, Added 2000-10-23, Author Jack Shirazi, Publisher O'Reilly). Tips: [Since the referred to page is already a summary list, I have not extracted it here. Especially since there are nearly 300 techniques listed. Check the page out statements, directly]. Comparing the performance of LinkedLists and ArrayLists (and Vectors) (Page last updated May 2001, Added 2001-06-18, Author Jack Shirazi, Publisher OnJava).
Tips: ArrayList is faster than Vector except when there is critiquing article, no lock acquisition required in HotSpot JVMs (when they have about the same performance). Vector and ArrayList implementations have excellent performance for indexed access and update of elements, since there is no overhead beyond range checking. Adding elements to, or deleting elements from the end of a Vector or ArrayList also gives excellent performance except when the capacity is exhausted and the internal array has to be expanded. Inserting and thesis issues deleting elements to 7 Vectors and ArrayLists always require an array copy (two copies when the issues, internal array must be grown first). The number of elements to be copied is proportional to [size-index], i.e. to scholarship application the distance between the insertion/deletion index and the last index in the collection. The array copying overhead grows significantly as the size of the collection increases, because the number of elements that need to be copied with each insertion increases. For insertions to Vectors and ArrayLists, inserting to the front of the collection (index 0) gives the thesis for controversial, worst performance, inserting at the end of the collection (after the how to, last element) gives the best performance. LinkedLists have a performance overhead for indexed access and update of elements, since access to any index requires you to traverse multiple nodes. LinkedList insertions/deletion overhead is statements for controversial issues, dependent on the how far away the insertion/deletion index is from the closer end of the collection. Synchronized wrappers (obtained from Collections.synchronizedList(List)) add a level of indirection which can have a high performance cost.
Only List and Map have efficient thread-safe implementations: the Vector and Hashtable classes respectively. List insertion speed is critically dependent on the size of the collection and essay for class 7 the position where the element is to be inserted. For small collections ArrayList and LinkedList are close in performance, though ArrayList is generally the faster of the two. Precise speed comparisons depend on the JVM and the index where the object is being added. Pre-sizing ArrayLists and Vectors improves performance significantly. LinkedLists cannot be pre-sized. Thesis For Controversial Issues? ArrayLists can generate far fewer objects for the garbage collector to reclaim, compared to LinkedLists.
For medium to large sized Lists, the location where elements are to inserted is critical to thesis on child rights the performance of the list. ArrayLists have the edge for random access. A dedicated List implementation designed to statements issues match data, collection types and data manipulation algorithms will always provide the best performance. ArrayList internal node traversal from the copy essay, start to the end of the statements for controversial issues, collection is essay on summer vacation 7, significantly faster than LinkedList traversal. Consequently queries implemented in the class can be faster. Iterator traversal of all elements is faster for ArrayList compared to Linkedlist.
Using the WeakHashMap class (Page last updated June 2001, Added 2001-07-20, Author Jack Shirazi, Publisher OnJava). Tips: WeakHashMap can be used to statements reduce memory leaks. Keys that are no longer strongly referenced from the application will automatically make the essays critiquing, corresponding value reclaimable. To use WeakHashMap as a cache, the keys that evaluate as equal must be recreatable. Using WeakHashMap as a cache gives you less control over thesis when cache elements are removed compared with other cache types. Clearing elements of a WeakHashMap is article, a two stage process: first the key is reclaimed, then the thesis statements for controversial issues, corresponding value is released from the WeakHashMap. String literals and other objects like Class which are held directly by the JVM are not useful as keys to a WeakHashMap, as they are not necessarily reclaimable when the essays, application no longer references them.
The WeakHashMap values are not released until the WeakHashMap is altered in some way. For Controversial? For predictable releasing of values, it may be necessary to add a dummy value to the WeakHashMap. If you do not call any mutator methods after populating the WeakHashMap, the critiquing article, values and internal WeakReference objects will never be dereferenced [no longer true from 1.4, where most methods now allow values to be released]. WeakHashMap wraps an internal HashMap adding an extra level of indirection which can be a significant performance overhead. [no longer true from 1.4]. Every call to get() creates a new WeakReference object. [no longer true from 1.4]. WeakHashMap.size() iterates through the keys, making it an operation that takes time proportional to the size of the WeakHashMap. [no longer true from thesis statements for controversial 1.4].
WeakHashMap.isEmpty() iterates through the collection looking for how to write unit, a non-null key, so a WeakHashMap which is statements issues, empty requires more time for isEmpty() to return than a similar WeakHashMap which is not empty. [no longer true from 1.4, where isEmpty() is now slower than previous versions]. A high level overview of of christmas, technical performance tuning, covering 5 levels of issues, tuning competence. Copy? (Page last updated November 2000, Added 2000-12-20, Author Jack Shirazi, Publisher O'Reilly). Tips: Start tuning by thesis issues examining the thesis rights in india, application architecture for potential bottlenecks. Architecture bottlenecks are often easy to spot: they are the connecting lines on thesis for controversial issues the diagrams; the single threaded components; the components with many connecting lines attached; etc. Ensure that application performance is measureable for the given performance targets. Ensure that there is of christmas, a test environment which represents the running system. This test-bed should support testing the application at different loads, including a low load and a fully scaled load representing maximum expected usage. After targeting design and architecture, the biggest bang for your buck in terms of thesis statements, improving performance is choosing a better VM, and then choosing a better compiler.
Start code tuning with proof of concept bottleneck removal: this consists of using profilers to identify bottlenecks, then making simplified changes which may only improve the write unit, performance at the bottleneck for a specialized set of activities, and proceeding to the next bottleneck. For Controversial? After tuning competence is gained, move to full tuning. How To Write Unit? Each multi-user performance test can typically take a full day to run and issues analyse. Essay On Summer For Class? Even simple multi-user performance tuning can take several weeks. Thesis For Controversial Issues? After the easily idenitified bottlenecks have been removed, the essays, remaining performance improvements often come mainly from targeting loops, structures and algorithms. In running systems, performance should be continually monitored to ensure that any performance degradation can be promptly identified and addressed. Chapter 4 of Java Performance Tuning, Object Creation. (Page last updated September 2000, Added 2000-10-23, Author Jack Shirazi, Publisher O'Reilly). Tips: Establish whether you have a memory problem. Statements? Reduce the scholarship application without essays, number of temporary objects being used, especially in loops. Avoid creating temporary objects within frequently called methods. Presize collection objects.
Reuse objects where possible. Empty collection objects before reusing them. (Do not shrink them unless they are very large.) Use custom conversion methods for thesis statements, converting between data types (especially strings and streams) to how to reduce the number of temporary objects. Thesis Statements Issues? Define methods that accept reusable objects to be filled in with data, rather than methods that return objects holding that data. (Or you can return immutable objects.) Canonicalize objects wherever possible. Compare canonicalized objects by essay for class 7 identity. [Canonicalizing objects means having only a single reference of an object, with no copies possible]. Create only the number of objects a class logically needs (if that is a small number of objects). Replace strings and other objects with integer constants. Compare these integers by identity. Use primitive data types instead of objects as instance variables. Avoid creating an object that is only for accessing a method. Flatten objects to reduce the number of thesis for controversial issues, nested objects. Preallocate storage for large collections of objects by mapping the instance variables into multiple arrays.
Use StringBuffer rather than the string concatenation operator (+). Without Essays? Use methods that alter objects directly without making copies. Thesis? Create or use specific classes that handle primitive data types rather than wrapping the primitive data types. Consider using a ThreadLocal to provide threaded access to singletons with state. Use the for class, final modifier on instance-variable definitions to create immutable internally accessible objects. Use WeakReference s to hold elements in large canonical lookup tables. (Use SoftReference s for cache elements.) Reduce object-creation bottlenecks by targeting the object-creation process. Keep constructors simple and inheritance hierarchies shallow. Avoid initializing instance variables more than once. Statements? Use the clone() method to avoid calling any constructors. Clone arrays if that makes their creation faster. Create copies of simple arrays faster by of christmas initializing them; create copies of complex arrays faster by cloning them.
Eliminate object-creation bottlenecks by moving object creation to statements for controversial an alternative time. Create objects early, when there is spare time in the application, and hold those objects until required. Use lazy initialization when there are objects or variables that may never be used, or when you need to distribute the load of creating objects. Use lazy initialization only when there is a defined merit in the design, or when identifying a bottleneck which is alleviated using lazy initialization. My article on basic optimizations for queries on collections (Page last updated September 2000, Added 2000-10-23, Author Jack Shirazi, Publisher O'Reilly). Tips: Use short-circuit boolean operators instead of the normal boolean operators. Eliminate any unnecessarily repeated method calls from critiquing loops. Eliminate unnecessary casts. Avoid synchronization where possible.
Avoid method calls by implementing queries in a subclass, allowing direct field access. Use temporary local variables to thesis statements for controversial issues manipulate data fields (instance/class variables). Copy Without? Use more precise object typing where possible. For Controversial? Before manual tuning, HotSpot VMs are often faster than JIT VMs. But JIT VMs tend to in india benefit more from manual tuning and can end up faster than HotSpot VMs. Article about optimizing queries on Maps. (Page last updated November 2000, Added 2000-12-20, Author Jack Shirazi, Publisher JavaWorld). Tips: Avoid using synchronization in read-only or single-threaded queries.
In the SDK, Enumerators are faster than Iterators due to the specific implementations. Eliminate repeatedly called methods where alternatives are possible. Iterator.hasNext() and Enumerator.hasMoreElements() do not need to be repeatedly called when the size of the collection is known. Use collection.size() and a loop counter instead. Avoid accessing collection data through the data access methods by implementing a query in the collection class. Elminate repeated casts by casting once and holding the cast item in a correctly typed variable. Reimplement the for controversial, collection class to specialize for the data being held in thesis in india the collection. Reimplment the statements, Map class to use a hash function which is more efficient for the data being mapped. Optimizing hash functions: generating a perfect hash function (Page last updated January 2001, Added 2001-02-21, Author Jack Shirazi, Publisher OnJava). Tips: perfect hash functions guarantee that every key maps to a separate entry in a hashtable, and so provide more efficient hastable implementations than generic hash functions. perfect hash functions are possible when the key data is thesis on child rights in india, restricted to a known set of elements. Optimize Map implementations by thesis statements specializing the on child, types of thesis for controversial, internal datastructures, and method parameter types and return types.
Optimize Map implementations by using a specialized hash function that is optimized for the key type, rather than generic to all possible types of keys. Generate a perfect hash function using some variable combination of simple arithmentic operators. Perfect hash functions may require excessive amounts of memory. Minimal perfect hash maps do not require any excess memory, but may impose significant overheads on the map. Microtuning (Page last updated March 2002, Added 2002-03-25, Author Jack Shirazi, Publisher OnJava). Tips: Performance is dependent on data as well as code. Different data can make identical code perform very differently. Always start tuning with a baseline measurement.
The System.currentTimeMillis() method is the most basic measuring tool for tuning. Scholarship Essays? You may need to thesis statements repeatedly call a method in order to reliably measure its average execution time. Minimize the possibility that CPU time will be allocated to essays critiquing anything other than the test while it is statements for controversial, running by ensuring no other processes are runing during the test, and that the test remains in critiquing the foreground. Baseline measurements normally show some useful information, e.g. the average execution time for one call to a method. Multiplying the average time taken to thesis for controversial execute a method or sequence of methods, by the number of times that sequence will be called in a time period, gives you an estimate of the fraction of the total time that the sequence takes.
There are three routes to tuning a method: Consider unexpected differences in different test runs; Analyze the algorithm; Profile the for class 7, method. Thesis Statements Issues? Creating an exception is a costly procedure, because of thesis rights, filling in stack trace. Thesis For Controversial? A profiler should ideally be able to essay vacation take a snapshot of issues, performance between two arbitrary points. Tuning is an iterative process: you normally find one bottleneck, make changes that improve performance, test those changes, and then start again. On Summer Vacation? Algorithm changes usually provide the statements for controversial issues, best speedup, but can be difficult to find. Examining the code for the causes of the differences in speed between two variations of test runs can be useful, but is restricted to those tests for which you can devise alternatives that show significant timing variations.
Profiling is always an option and almost always provides something that can be speeded up. On Summer Vacation 7? But the law of diminishing returns kicks in after a while, leaving you with bottlenecks that are not worth speeding up, because the potential speedup is too small for statements for controversial issues, the effort required. Generic integer parsing (as with the Integer constructors and methods) may be overkill for converting simple integer formats. Thesis Rights? Simple static methods are probably best left to statements for controversial issues be inlined by the JIT compiler rather than by hand. String.equals() is expensive if you are only testing for without, an empty string. It is quicker to test if the thesis statements for controversial issues, length of the string is 0. Set a target speedup to reach. With no target, tuning can carry on critiquing for much longer than is needed. A generic tuning procedure is: Identify the bottleneck; Set a performance target; Use representative data; Measure the baseline; Analyze the method; Test the change; Repeat. Efficiently formatting doubles (Page last updated December 2000, Added 2000-12-20, Author Jack Shirazi, Publisher OnJava).
Tips: Double.toString(double) is statements, slow. It needs to process more than you might think, and does more than you might need. Proprietary conversion algorithms can be significantly faster. One such algorithm is presented in the article. How To? Converting integers to strings can also be faster than the SDK. Thesis Issues? An algorithm successively stripping off the highest is used in the article. Formatting numbers using java.text.DecimalFormat is always slower than Double.toString(double), because it first calls Double.toString(double) then parses and converts the essay, result. Formatting using a proprietary conversion algorithm can be faster than any of the methods discussed so far, if the number of digits being printed is issues, not large. The actual time taken depends on how to write unit the number of digits being printed.
Multiprocess JVMs (Page last updated September 2001, Added 2001-10-22, Author Jack Shirazi, Publisher OnJava). Statements For Controversial Issues? Tips: Using or implementing a multiprocess framework to without combine Java processes into one JVM can save on issues memory space overheads and reduce startup time. Measuring JDBC performance (Page last updated December 2001, Added 2001-12-26, Author Jack Shirazi, Publisher OnJava). Tips: Effectively profiling distributed applications can be difficult. I/O can show up as significant in profiling, simply because of the nature of a distributed application. It can be unclear whether threads blocking on reads and writes are part of a significant bottleneck or simply a side issue. When profiling, it is usually worthwhile to critiquing article have separate measurements available for thesis statements for controversial, the communication subsystems. Wrapping the JDBC classes provides an effective technique for measuring database calls. Critiquing? [Article discusses how to for controversial create JDBC wrapers to measure the performance of database calls]. If more than a few rows of a query are being read, then the ResultSet.next() method can spend a significant amount of critiquing article, time fetching rows from the statements for controversial issues, database, and how to this time should be included in measurements of database access. JDBC wrappers are simple and for controversial issues robust, and require very little alteration to the application using them (i.e, are low maintenance), so they are suitable to be retained within a deployed application.
Catching OutOfMemoryErrors (Page last updated August 2001, Added 2001-10-22, Author Jack Shirazi, Publisher OnJava). Tips: -Xmx and -Xms (-mx and application without -ms) specify the statements, heap max and starting sizes. Runtime.totalMemory() gives the current process size, Runtime.maxMemory() (available from SDK 1.4) gives the -Xmx value. Repeatedly allocating memory by write unit creating objects and holding onto them will expand the process to its maximum possible size. This technique can also be used to flush memory. If a process gets too large, the operating system will start paging the process causing a severe decrease in performance. It is reasonable to catch the thesis statements, OutOfMemoryError if you can restore your application to a known state that can proceed with processing. For example, daemon service threads can often do this. The RandomAccess interface. (Page last updated October 2001, Added 2001-11-27, Author Jack Shirazi, Publisher OnJava). Tips: A java.util.List object which implements RandomAccess should be faster when using List.get() than when using Iterator.next(). Use instanceof RandomAccess to test whether to use List.get() or Iterator.next() to traverse a List object. [Article describes how to copy without guard the test to thesis statements issues support all versions of essay on summer vacation for class, Java].
Whoopee!! A non-blocking I/O library for Java. This is the single most important functionality missing from the SDK for thesis statements for controversial, scalable server applications. The important class is SelectSet which allows you to multiplex all your i/o streams. Thesis? If you want a scalable server and can use this class then DO SO. NOTE THAT SDK 1.4 WILL INCLUDE NON_BLOCKING I/O (Page last updated March 2001, Added 2001-01-19, Author Matt Welsh, Publisher Welsh). Statements For Controversial? Tips: [The system select(2)/poll(2) functions allow you to how to unit take any collection of i/o streams and ask the operating system to check whether any of them can execute read/write/accept without blocking. Thesis Issues? The system call will block if requested until any one of the i/o streams is ready to execute. Before Java, no self-respecting server would sit on multiple threads in application without essays blocked i/o mode, wasting thread resources: instead select/poll would have been used.] For years, Jonathan Hardwick's old but classic site was the only coherent Java performance tuning site on the web.
He built it while doing his PhD. It wasn't updated beyond March 1998, when he moved to Microsoft, but most tips are still useful and valid. Thesis Statements For Controversial Issues? The URL is for the top page, there are another eight pages. Thanks Jonathan. (Page last updated March 1998, Added 2000-10-23, Author Jonathan Hardwick, Publisher Hardwick). Scholarship Application? Tips: Don't optimize as you go. Write your program concentrating on clean, correct, and thesis statements for controversial understandable code. Use profiling to find out where that 80% of execution time is going, so you know where to concentrate your effort. Always run before and essays after benchmarks.
Use the right algorithms and data structures. Statements For Controversial? Compile with optimization flag, javac -O. Use a JIT. Multithread for multi-processor machines. Use clipping to reduce the amount of work done in repaint() Use double buffering to improve perceived speed. Use image strips or compression to speed up downloading times.
Animation in Java Applets from JavaWorld and copy essay Performing Animation from Sun are two good tutorials. Use high-level primitives; it's much faster to call drawPolygon() on thesis for controversial a bunch of points than looping with drawLine(). If you have to draw a single pixel drawLine (x,y,x,y) may be faster than fillRect (x,y,1,1). Use Buffered I/O classes. Avoid synchronized methods if you can. Essays? Synchronizing on methods rather than on code blocks is slightly faster. Use exceptions only statements for controversial issues, where you really need them. Essays Article? Use StringBuffer instead of +. Thesis Statements For Controversial Issues? Use System.arraycopy() and thesis on child rights in india any other optimized API's available from the SDK. Thesis Statements? Replace the generic standard classes with faster implementations specific to the application. Create subclasses to how to unit override methods with faster versions.
Avoid expensive constructs and data structures, e.g. Statements For Controversial? one-dimensional array is faster than a two-dimensional array. Thesis On Child? Use the faster switch bytecode. Use private and static methods, and final classes, to encourage inlining by the compiler. Reuse objects. Statements For Controversial? Local variables are the faster than instance variables, which are in turn faster than array elements. Write Unit? ints are the fastest data type. Issues? Compiler optimizations: loop invariant code motion; common subexpression elimination; strength reduction; variable allocation reassignment. Without? Use java -prof or other profiler. Use a timing harness to run benchmarks. Use a memory measurement harness to thesis statements for controversial run benchmarks.
Call system.gc() before every timing run to minimize inconsistent results due to garbage collection in the middle of a run. Rights In India? Use JAR or zip files. If size is thesis statements, a constraint: use SDK classes wherever possible; inherit whatever possible; put common code in one place; initialize big arrays at runtime by parsing a string; use short names; Balancing Network Load with Priority Queues (Page last updated December 2001, Added 2002-02-22, Author Frank Fabian, Publisher Dr. Dobb's).
Tips: Hardware traffic managers redirect user requests to a farm of essays of christmas, servers based on server availability, IP address, or port number. All traffic is statements issues, routed to how to write unit the load balancer, then requests are fanned out to servers based on the balancing algorithm. Popular load-balancing algorithms include: server availability (find a server with available processing capability); IP address management (route to the nearest server by for controversial issues IP address); port number (locate different types of servers on different machines, and route by port number); HTTP header checking (route by URI or cookie, etc). Web hits should cater for handling peak hit rate, not the average rate. You can model hit rates using gaussian distribution to determine the average hit rate per time unit (e.g. per second) at peak usage, then a poisson probability gives the probability of a given number of users simulatneously hitting the server within that time unit. [Article gives an example with gaussian fitted to peak traffic of how to write unit, 4000 users with a standard deviation of 20 minutes resulting in an average of 1.33 users per second at issues the peak, which in turn gives the probabilities that 0, 1, 2, 3, 4, 5, 6 users hitting the application without, server within one second as 26%, 35%, 23%, 10%, 3%, 1%, 0.2%.
Service time was 53 milliseconds, which means that the thesis statements, server can service 19 hits per second without the service rate requiring requests being queued.] System throughput is the of christmas, arrival rate divided by the service rate. If the thesis for controversial issues, ratio becomes greater than one, requests exceed the on child in india, system capability and will be lost or need to be queued. If requests are queued because capacity is exceeded, the throughput must drop sufficiently to handle the thesis issues, queued requests or the system will fail (the service rate must increase or arrival rate decrease). If the essay on summer vacation for class, average throughput exceeds 1, then the system will fail. Sort incoming requests into thesis statements for controversial issues different priority queues, and service the requests according to the priorities assigned to each queue. [Article gives the example where combining user and automatic requests in one queue can result in a worst case user wait of 3.5 minutes, as opposed to essay on summer for class less than 0.1 seconds if priority queues are used]. Statements? [Note that Java application servers often do not show a constant service time. Essays Critiquing Article? Instead the service time often increases with higher concurrency due to non-linear effects of thesis statements, garbage collection].
Cutting Edge Java Game Programming. Oldish but still useful intro book to games programming using Java. Copy? (Page last updated 1996, Added 2001-06-18, Author Neil Bartlett, Steve Simkin , Publisher Coriolis). Tips: AWT components are not useful as game actors (sprites) as they do not overlap well, nor are they good at statements for controversial being moved around the of christmas, screen. Celled image files efficiently store an for controversial issues animated image by essays dividing an image into a rectangular grid of thesis, cells, and allocating a different animation image to how to each cell. A sequence of similar images (as you would have for an animation) will be stored and transferred efficiently in most image formats.
Examining pixels using PixelGrabber is slow. drawImage() can throw away and re-load images in response to memory requirements, which can make things slow. Pre-load and pre-scale images before using them to get a smoother and faster display. The more actors (sprites), the more time it takes to for controversial draw and the slower the game appears. Use double-buffering to move actors (sprites), by redrawing the actor and background for the relevant area. Redraw speed depends on: how quickly each object is drawn; how many objects are drawn; how much of each object is drawn; the total number of essays article, drawing operations. You need to issues reduce some or all of these until you get to about 30 redraws per essay on summer vacation for class, second. Don't draw actors or images that cannot be seen. If an actor is not moving then incorporate the actor as part of the background. For Controversial Issues? Only redraw the essays, area that has changed, e.g. the old area where an actor was, and the new area where it is.
Redrawing several small areas is frequently faster than drawing one large area. For the redraws, eliminate overlapping areas and merge adjacent (close) areas so that the number of redraws is kept to thesis statements a minimum. For Class 7? Put slow and statements for controversial issues fast drawing requirements in separate threads. Bounding-box detection can use circles for the bounding box which requires a simple radii detection. Load sounds in a background thread.
Make sure you have a throttle control that can make the game run slower (or pause) when necessary. Essay On Summer For Class 7? The optimal network topology for network games depends on the number of thesis issues, users. If the without, cumulative downloading of your applet exceeds the issues, player?s patience, you?ve lost a customer. The user interface should always be responsive. On Child? A non-responsive window means you will lose your players. Give feedback on necessary delays. Provide distractions when unavoidable delays will be lengthy [more than a few seconds]. Transmission time varies, and is always slow compared to operations on the local hardware. You may need to thesis statements issues decide the outcome of the action locally, then broadcast the result of the action.
This may require some synchronization resolution. Latency between networked players can easily lead to de-synchronized action and player frustration. Displays should locally simulate remote action as continuing current activities/motions, until the display is updated. Essays Of Christmas? On update, the actual current situation should be smoothly resolved with the simulated current situation. Sending activity updates more frequently ensures smoother play and better synchronization between networked players, but requires more CPU effort and so affects the for controversial, local display. Scholarship Application Without? In order to avoid adversely affecting local displays, send actvity updates from a low priority thread. Statements? Discard any out-of-date updates: always use the essays of christmas, latest dated update. For Controversial Issues? A minimum broadcast delay of one-third the average network connection travel time is appropriate.
Once you exceed this limit, the additional traffic can cause more grief than benefit. Put class files into a (compressed) container for network downloading. Avoid repeatedly evaluating invariant expressions in a loop. Take advantage of inlining where possible (using final, private and static keywords, and compiling with javac -O) Profile the code to determine the expensive methods (e.g. Essays? using the -prof option) Use a dissassembler (e.g. like javap) to determine which of thesis for controversial issues, various alternative coding formulations produces smaller bytecode. To reduce the number of class files and copy essay their sizes: use the SDK classes as much as possible; and implement common functionality in one place only.
To optimize speed: avoid synchronized methods; use buffered I/O; reuse objects; avoid unnecessary screen painting. Raycasting is faster than raytracing. Raycasting maps 2D data into a 3D world, drawing entire vertical lines using one ray. Use precalculated values for trignometric and other functions, based on the angle increments chosen for your raycasting. Thesis Statements? In the absence of a JIT, the polygon drawing routines fron the how to write, AWT are relatively efficient (compared to array manipulation) and may be faster than texture mapping. Without texture mapping, walls can be drawn faster with one call to fillPolygon (rather than line by line). An exponential jump search algorithm can be used to reduce ray casts - by quickly finding boundaries where walls end (like a binary search, but double increments until your overshoot, then halving increments from the last valid wall position). It is usually possible to increase performance at the expense of image quality and accuracy.
Techniques include reducing pixel depth or display resolution, field interlacing, aliasing. The key, however, is to thesis statements for controversial issues degrade the image in a way that is likely to essays critiquing article be undetectable or unnoticeable to the user. For example a moving player often pays less attention to image quality than a resting or static player. Use information gathered during the rendering of one frame to approximate the geometry of the next frame, speeding up its rendering. If the geometry and content is statements, not too complicated, binary space partition trees map the view according to what the player can see, and can be faster than ray casting. Designing remote interfaces (Page last updated March 2001, Added 2001-04-20, Author Brian Goetz, Publisher JavaWorld). Tips: Remote object creation has overheads: several objects needed to support the essay on summer vacation, remote object are also created and manipulated. Remote method invocations involve a network round-trip and marshalling and unmarshaling of parameters. Statements? This adds together to impose a significant latency on essays remote method invocations.
Different object parameters can have very different marshalling and thesis statements unmarshaling costs. A poorly designed remote interface can kill a program's performance. Rights? Excessive remote invocation network round-trips are a huge performance problem. Calling a remote method that returns multiple values contained in a temporary object (such as a Point), rather than making multiple consecutive method calls to retrieve them individually, is likely to thesis statements for controversial issues be more efficient. (Note that this is exactly the opposite copy essay of the for controversial, advice offered for good performance of critiquing, local objects.) Avoid unnecessary round-trips: retrieve several related items simultaneously in one remote invocation, if possible. Issues? Avoid returning remote objects when the caller may not need to hold a reference to the remote object. Avoid passing complex objects to remote methods when the on summer vacation, remote object doesn't necessarily need to have a copy of the object.
If a common high-level operation requires many consecutive remote method calls, you need to revisit the class's interface. A naively designed remote interface can lead to statements issues an application that has serious scalability and performance problems. [Article gives examples showing the effect of applying the listed advice]. Glen McCluskey's paper with 30 tuning tips, now free. (Page last updated October 1999, Added 2000-10-23, Author Glen McCluskey, Publisher McCluskey). Tips: Faster algorithms are better. Different architectures can be functionally identical but perform very differently. Essays? Keep performance in mind at the design stage. Use the fastest available JVM.
Use static variables for fields that only need to be assigned once. Reuse objects where reasonable, e.g. nodes of thesis statements issues, a linked list. Inline methods manually where appropriate. [Better to critiquing article use a preprocessor]. Keep methods short and simple to make them automatic inlining candidates. final classes can be faster. Synchronized methods are slower than the identical non-synchronized one. Statements For Controversial? Consider using non-synchronized classes and synchronized-wrappers. Access to private members of inner classes from the enclosing class goes by essay on summer vacation 7 a method call even if not intended to. Statements For Controversial? Use StringBuffer instead of the '+' String concatentation operator. Use char arrays directly to how to write create Strings rather than StringBuffers. Statements Issues? '==' is faster than equals(). intern() Strings to essays enable identity (==) comparisons. Convert strings to char arrays to process characters, rather than accessing characters one at a time using String.charAt().
Creating Doubles from strings is slow. Buffer i/o. MessageFormat is slow. Reuse objects. Statements For Controversial? File information such as File.length() requires a system call and can be slow.
Use System.arraycopy() to copy arrays. ArrayList is faster than Vector. Preset array capacity to as large as will be required. Scholarship? LinkedList is faster than ArrayList for thesis statements for controversial issues, inserting elements to the front of the array, but slower at indexed lookup. Program using interfaces so that the actual structure can be easily swapped to improve performance. Use the -g:none option to the javac compiler. Primitive data wrapper classes (e.g. Integer) are slower than using the without, primitive data directly. Null out references when they are no longer used so that garbage collection can reclaim their space. Use SoftReferences to recycle memory when required.
BitSets have deterministic memory requirements where boolean arrays do not (booleans are implemented as bytes rather than bits in some JVMs). Use sparse arrays to hold widely spaced indexable data. Performance tuning part of statements for controversial, a white paper about Java on Solaris 2.6. (Page last updated 2000, Added 2000-10-23, Author ?, Publisher Sun). Tips: To profile I/O calls, use a profiler or use truss and look for read() and write() system calls. Essays Of Christmas? Buffer I/O. Tune the buffer size (bigger is usually better if memory is available). Use char arrays for all character processing in loops, rather than using the String or StringBuffer classes. Avoid character processing using methods (e.g. Thesis Statements Issues? charAt(), setCharAt()) inside a loop.
Set the initial StringBuffer size to the maximum string length, if it is known. StringTokenizer is very inefficient, and can be optimized by without storing the thesis, string and delimiter in without a character array instead of in String, or by storing the highest delimiter character to thesis statements for controversial issues allow a quicker check. Accessing arrays is much faster than accessing vectors, String, and thesis StringBuffer. Use System.arraycopy() to improve performance. For Controversial? Vector is convenient to use, but inefficient. Essays Article? Ensure that elementAt() is thesis for controversial, not used inside a loop. Essays? FastVector is faster than Vector by issues making the elementData field public, thus avoiding (synchronized) calls to elementAt().
Use double buffering and on summer vacation for class 7 override update() to for controversial issues improve screen painting and drawing. Use custom LayoutManagers. Repaint only the damaged regions (use ClipRect). To improve image handling: use MediaTracker; use your own imageUpdate() method; pre-decode and store the essays of christmas, image in thesis for controversial an array - image decoding time is greater than loading time. Pre-decoding using PixelGrabber and MemoryImageSource should combine multiple images into one file for maximum speed. Increase the initial heap size from the 1-MByte default with -ms and -mx [-Xms and -Xmx]. Use -verbosegc.
Take size into on child rights in india account when allocating arrays (for instance, if short is big enough, use it instead of for controversial, int. Avoid allocating objects in loops (readLine() is a common example). Minimize synchronization. Polling is essays, only acceptable when waiting for outside events and should be performed in a side thread. Use wait/notify instead. Move loop invariants outside the loop. Make tests as simple as possible. Perform the loop backwards (this actually performs slightly faster than forward loops do). [Actually it is converting the test to compare against 0 that makes the difference]. For Controversial Issues? Use only local variables inside a loop; assign class fields to local variables before the on child in india, loop.
Move constant conditionals outside loops. Combine similar loops. Nest the busiest loop, if loops are interchangeable. For Controversial Issues? Unroll the loop, as a last resort. Thesis On Child In India? Convert expressions to table Lookups. Use caching. Pre-compute values or delay evaluation to shift calculation cost to another time. [Also gives information on statements for controversial using Solaris Trace Normal Format (TNF) utilities for profiling java applications].
Detailed article on load testing systems (Page last updated January 2001, Added 2001-01-19, Author Himanshu Bhatt, Publisher Java Report). Tips: Internet systems should be load-tested throughout development. Load testing can provide the basis for: Comparing varying architectural approaches; Performance tuning; Capacity planning. Initially you should identify the of christmas, probable performance and scalability based on the requirements. Statements For Controversial? You should be asking about: numbers of users/components; component interactions; throughput and write transaction rates; performance requirements. Factor in batch requirements and performance characteristics of dependent (sub)systems. Note that additional layers, like security, add overheads to performance.
Logging and stateful EJB can degrade performance. After the initial identification phase, the target should be for a model architecture that can be load-tested to feedback information. Scalability hotspots are more likely to statements for controversial issues exist in the tiers that are shared across multiple client sessions. Performance measurements should be from presentation start to presentation completion, i.e. user clicks button (start) and information is displayed (completion). Use load-test suites and frameworks to perform repeatable load testing. Article on using syslog to scholarship application without track performance across distributed systems (Page last updated December 2000, Added 2001-01-19, Author Brian Maso, Publisher DevX). Tips: Use syslog to log distributed system performance. Make sure you instrument distributed systems so that you do get performance logging.
JDBC Performance Tips (targeted at thesis statements for controversial issues AS/400, but generically applicable) (Page last updated February 2001, Added 2001-03-21, Authors Richard Dettinger and Mark Megerian, Publisher IBM). Tips: Move to the latest releases of critiquing, Java as they become available. Use prepared statements (PreparedStatement class) [article provides coded example of using Statement vs. Statements For Controversial? PreparedStatement]. Note that two database calls are made for each row in a ResultSet: one to write describe the column, the second to thesis for controversial issues tell the db where to put the data.
PreparedStatements make the description calls at construction time, Statements make them on every execution. Avoid retrieving unnecessary columns: don't use SELECT *. If you are not using stored procedures or triggers, turn off autocommit. All transaction levels operate faster with autocommit turned off, and article doing this means you must code commits. Coding commits while leaving autocommit on will result in extra commits being done for thesis for controversial issues, every db operation. Use the appropriate transaction level. Increasing performance costs for transaction levels are: TRANSACTION_NONE; TRANSACTION_READ_UNCOMMITTED; TRANSACTION_READ_COMMITTED; TRANSACTION_REPEATABLE_READ; TRANSACTION_SERIALIZABLE. Essays? Note that TRANSACTION_NONE, with autocommit set to statements for controversial true gives access to triggers, stored procedures, and thesis rights large object columns.
Store string and thesis statements for controversial char data as Unicode (two-byte characters) in the database. Avoid expensive database query functions such as: getBestRowIdentifier; getColumns; getCrossReference; getExportedKeys; getImportedKeys; getPrimaryKeys; getTables; getVersionColumns. Use connection pooling, either explicitly with your own implementation, or implicitly via a product that supports connection pooling. Use blocked fetchs (fetching table data in blocks), and essays critiquing article tailor the block size to reduce calls to the database, according to the amount of data required. Use batch updates (sending multiple rows to the database in one call). Use stored procedures where appropriate. These benefit by reducing JDBC complexity, are faster as they use static SQL, and move execution to the server and potentially reduce network trips. Use the type-correct get() method, rather than getObject(). Patrick Killelea's Java performance tips. (Page last updated 1999, Added 2000-10-23, Author Patrick Killelea, Publisher Killelea). Tips: System.currentTimeMillis may take up to 0.5 milliseconds to execute.
The architecture and statements for controversial issues algorithms of your program are much more important than any low-level optimizations you might perform. Tune at of christmas the highest level first. Make the common case fast (Amdahl's advice). Statements For Controversial Issues? Use what you know about the runtime platform or usage patterns. Look at a supposedly quiet system to see if it's wasting time even when there's no input. Essay Without? Keep small inheritance chains. Thesis? Use stack (local) variables in preference to essays class variables. Merge classes. drawPolygon() is statements, faster than using drawLine() repeatedly. Don't create too may objects. Rights? Reuse objects if possible. Issues? Beware of on child in india, object leaks (references to objects that are never nulled).
Accessor methods increase overhead. Compound operators such as n += 4; are faster than n = n + 4; because fewer bytecodes are generated. Shifting by powers of two is faster than multiplying. Thesis For Controversial Issues? Multiplication is faster than exponentiation. int increments are faster than byte or short increments. Floating point increments are much slower than any integral increment. Memory access from essays of christmas better to worse: local vars; supersuperclass instance variable; superclass instance var; class instance var; class static var; array elements. It can help to copy slower-access vars to fast local vars if you are going to operate on them repeatedly, as in a loop. Use networking timeouts, TCP_NODELAY, SO_TIMEOUT, especially in case of dying DNS servers. Buffer network io. [or read explicitly in chunks]. Issues? Avoid reverse DNS where you can. Use UDP rather than TCP if speed is more important than accuracy.
Use threads. Critiquing Article? Prioritize threads. Use notify instead of notifyAll. Use synchronization sparingly. Counting down is often faster than counting up. [the loop test comparison to 0 is what matters]. Statements For Controversial Issues? Keep synchronized methods out of loops if you possibly can. Avoid excessive String manipulation. Use String Buffers or Arrays rather than String. byte arrays may be faster than StringBuffers for certain operations, especially if you use System.arraycopy(). Use StringBuffer rather than the + operator. Watch out for slow fonts, Fonts vary in speed of rendering. Copy Essay? Keep the paint method small.
It will get called a lot. Thesis Statements Issues? Double buffer where possible. For some applications that access the date a lot, it can help to set the copy essay, local timezone to be GMT, so that no conversion has to take place. Statements For Controversial? Potential compiler optimizations: loop invariant code motion; common subexpression elimination; strength reduction; variable allocation. Don't turn off native threads. Use .jar files.
Rewrite Java library classes to without essays make them smaller or instantiate fewer objects or eliminate synchronization. Thesis Statements For Controversial? Install classes locally. Tutorial on on summer for class 7 the full screen capabilities in the 1.4 release (5 pages plus example pages under the top page) (Page last updated June 2001, Added 2001-06-18, Author Michael Martak, Publisher Sun). Tips: The full-screen exclusive mode provides maximum image display and drawing performance by thesis for controversial issues allowing direct drawing to the screen. Use java.awt.GraphicsDevice.isFullScreenSupported() to determine if full-screen exclusive mode is available. If it is write unit, not available, full-screen drawing can still be used, but better performance will be obtained by thesis for controversial using a fixed size window in normal screen mode. Full-screen exclusive applications should not be resizable. Thesis? Turn off decoration using the setUndecorated() method. Change the screen display mode (size, depth and refresh rate), to the best match for statements, your image bit depth and display size so that scaling and other image alterations can be avoided or minimized.
Don't define the screen painting code in the paint() method called by the AWT thread. Define your own rendering loop for screen drawing, to be executed in any thread other than the AWT thread. Use the critiquing article, setIgnoreRepaint() method on your application window and components to turn off all paint events dispatched from the operating system completely, since these may be called during inappropriate times, or worse, end up calling paint, which can lead to race conditions between the AWT event thread and issues your rendering loop. Do not rely on the update or repaint methods for delivering paint events. Do not use heavyweight components, since these will still incur the overhead of essays, involving the statements for controversial, AWT and the platform's windowing system. Use double buffering (drawing to unit an off-screen buffer, then copying the finished drawing to the screen). Use page-flipping (changing the video pointer so that an thesis for controversial off-screen buffer becomes the on-screen buffer, with no image copying required). Use a flip chain (a sequence of off-screen buffers which the essay on summer vacation 7, video pointer successively points to one after the other). Statements For Controversial Issues? java.awt.image.BufferStrategy provides getDrawGraphics() (to get an on summer vacation off-screen buffer) and show() (to display the buffer on screen). Use java.awt.BufferCapabilities to customize the BufferStrategy for statements for controversial, optimizing the performance of your application.
If you use a buffer strategy for double-buffering in a Swing application, you probably want to essays of christmas turn off double-buffering for your Swing components, Multi-buffering is only useful when the drawing time exceeds the time spent to issues do a show. Unit? Don't make any assumptions about performance: profile your application and identify the bottlenecks first. HP Java tuning site, including optimizing Java and optimizing HPUX for Java. This is the top page, but several useful pages lie off it (tips extracted for inclusion below). Includes a nice procedure list for tuning apps, and some useful forms for what you should record while tuning. (Page last updated 2000, Added 2000-10-23, Author ?, Publisher HP). Tips: Have a performance target.
Consider architecture and for controversial issues components for bottlenecks. Third-party components may have options that cause bottlenecks. Having debugging turned on can cause performance problems. Essays? Having logging turned on can cause performance problems. Is the underlying machine powerful enough. Carefully document any tests and changes.
Create a performance baseline. Make one change at a time. Be careful not to lose a winning tune because it's hidden by a bad tune made at thesis issues the same time. Write Unit? Record all aspects of the system (app/component/version/version date/dependent software/CPU/Numbers of CPUs/RAM/Disk space/patches/OS config/etc.) Give the JVMs top system priority. Tune the heap size (-mx, -ms options) and use -verbosegc to minimize garbage collection impact. A larger heap reduces the frequency of garbage collection but increases the length of thesis for controversial, time that any particular garbage collection takes.
Rules of thumbs are: 50% of free space available after a gc; set the maximum heap size to be 3-4 times the space required for the estimated maximum number of live objects; set the initial heap to size a little below the space required for the average data set, and the maximum value large enough to handle the how to, largest data set; increase -Xmn for applications that create many short-lived objects [is -Xmn a standard option?]. [These rules of thumb should only statements for controversial issues, be considered as starting points. Ultimately you need to essays of christmas tune the VM heap empirically, i.e. by trial and error]. You may need to add flags to third party products running in the JVM to eliminate explicit calls to garbage collect (VisiBroker has this known problem). Watch out for bottlenecks introduced from third party products. Make sure you know and use the options available, many of thesis for controversial issues, which can affect performance (for better or worse). Write? Document the thesis issues, changes you make so that you will be able to reproduce the performance. computationally intensive applications should increase the essays of christmas, number of CPUs to increase overall system performance and throughput. Be certain that the thesis statements for controversial, application's CPU usage is a factor limiting performance: often, highly contended locks and garbage collections that are too frequent will make the system look busy, but little work is copy essay without, done by the application. [Some nice detailed description on thesis issues how to profile and scholarship without essays analyze application problems, from the HP system and JVM level at http://www.devresource.hp.com/JavaATC/JavaPerfTune/symptoms_solutions.html.] J2EE Application server performance (Page last updated April 2001, Added 2001-04-20, Author Misha Davidson, Publisher Java Developers Journal). Tips: Good performance has sub-second latency (response time) and hundreds of (e-commerce) transactions per second.
Avoid n-way database joins: every join has a multiplicative effect on the amount of thesis statements for controversial, work the database has to essay do. The performance degradation may not be noticeable until large datasets are involved. Avoid bringing back thousands of rows of data: this can use a disproportionate amount of resources. Cache data when reuse is likely. Statements? Avoid unnecessary object creation. Minimize the use of synchronization. Avoid using the SingleThreadModel interface for servlets: write thread-safe code instead. ServletRequest.getRemoteHost() is very inefficient, and can take seconds to complete the essay for class 7, reverse DNS lookup it performs. OutputStream can be faster than PrintWriter. JSPs are only generally slower than servlets when returning binary data, since JSPs always use a PrintWriter, whereas servlets can take advantage of thesis statements for controversial issues, a faster OutputStream. Scholarship Application Without Essays? Excessive use of custom tags may create unnecessary processing overhead.
Using multiple levels of BodyTags combined with iteration will likely slow down the processing of the page significantly. Statements For Controversial? Use optimistic transactions: write to rights the database while checking that new data is thesis statements for controversial, not be overwritten by using WHERE clauses containing the thesis on child in india, old data. However note that optimistic transactions can lead to worse performance if many transactions fail. Statements Issues? Use lazy-loading of dependent objects. Scholarship Without? For read-only queries involving large amounts of thesis statements issues, data, avoid EJB objects and use JavaBeans as an intermediary to access manipulate and store the data for JSP access. Use stateless session EJBs to essay without cache and manage infrequently changed data. Update the EJB occasionally.
Use a dedicated session bean to perform and cache all JNDI lookups in a minimum number of requests. Minimize interprocess communication. Use clustering (multiple servers) to increase scalability. Using the statements, Syslog class for logging (Page last updated April 2001, Added 2001-04-20, Author Nate Sammons, Publisher JavaWorld). Tips: Use Syslog to log system performance. Logging should not take up a significant amount of the system's resources nor interfere with its operation. Use static final boolean s to wrap logging statements so that they can be easily turned off or eliminated.
Beware of logging to slow external channels. Copy Without? These will slow down logging, and hence the application too. Glen McCluskey's article on tuning Java I/O performance. Weak on serialization tuning. (Page last updated March 1999, Added 2000-10-23, Author Glen McCluskey, Publisher Sun). Tips: Avoid accessing the statements for controversial issues, disk. Essays Of Christmas? Avoid accessing the underlying operating system. Avoid method calls. Avoid processing bytes and characters individually. Use buffering either at the class level or at statements for controversial issues the array level. Disable line buffering.
MessageFormat is slow. Reuse objects. Creating a buffered RandomAccessFile class can be faster than plain RandomAccessFile if you are seeking alot. Compression can help I/O, but only write unit, sometimes. Use caching to speed I/O. Thesis Statements? Your own tokenizer will be faster than using the available SDK tokenizer. Many java.io.File methods are system calls which can be slow. Designing Entity Beans for Improved Performance (Page last updated March 2001, Added 2001-03-21, Author Beth Stearns, Publisher Sun). Tips: Remember that every call of an essays of christmas entity bean method is potentially a remote call.
Designing with one access method per data attribute should only be used where remote access will not occur, i.e. entities are guaranteed to be in the same container. Use a value object which encapsulates all of an entity's data attributes, and statements for controversial issues which transfers all the data in one network transfer. This may result in large objects being transferred though. Group entity bean data attributes in of christmas subsets, and use multiple value objects to provide remote access to those subsets. Performance tuning report in German. Thanks to thesis for controversial issues Peter Kofler for extracting the tips. On Summer Vacation For Class 7? (Page last updated November 2001, Added 2001-07-20, Author Sebastian Ritter, Publisher Ritter). Tips: Performance optimizations vary in effect on thesis different platforms. Always test for your platforms. Reasons not to optimize: can lead to unreadable source code; can cause new errors; optimizations are often compiler/JVM/platform dependent; can lose object orientation. Scholarship Essays? Reasons to thesis statements issues optimize: application uses too much memory/processor/I/O; application is unnaceptably slow. Don't optimize before you have at critiquing least a functioning prototype and for controversial some identified bottlenecks.
Try to optimize the essays, design first before targeting the implementation. Profile applications. Use the 80/20 rull which suggests that 80% of the work is thesis statements issues, done in 20% of the code. Target loops in particular. Essays? Monitor running applications to maintain performance. Plan and thesis budget for some resources to optimize the application. Try to have or develop a couple of performance experts. Application Without Essays? Specify performance in the project requirements, and statements for controversial specify seperate performance requirements for the various layers of the application. Consider the effects of essay vacation 7, performance at the analysis stage, and include testing of thesis statements for controversial issues, 3rd party tools. Use a benchmark harness to make repeatable performance tests, varying the scholarship application essays, number of thesis for controversial issues, users, data, etc.
Use profilers and logging to unit measure performance and for controversial identify performance problems. Optimize the runtime system if the optimization does not require alterations to the application design or implementation. Test various JVMs and choose the optimal JVM. JIT compilers are faster but require more memory than interpreter JVMs. HotSpot can provide better performance and a faster startup and maintain a relatively low memory requirement. Essays? Design in thesis statements for controversial issues asynchronous operations so tasks are not waiting for others to finish when they don't need to. use the right VM use the right threading model (native vs. Essay On Summer For Class? green) use native compilers give more ram to the VM give all ram to short-lived applications to completely avoid GC use alternate/optimizing compilers use the right database driver use direct JDBC drivers expand all JDK classes into the filesystem to increase access to classes use slot-local variables (1st 128 bit = 4 slots) (applies for statements issues, interpreters only) use int use Arraylist instead of Vector use own Hashtable implementations for primitives (i.e. int) use caches use object pools avoid remote method calls use callbacks to avoid blocking remote method calls use batching for remote method calls use the flyweight pattern to copy reduce object creation [The flyweight pattern uses a factory instead of thesis, 'new' to reuse objects rather than always create new ones]. use the rights, right access modifier: static private final protected public use inlining use shallow hierarchies (to avoid long instantiation chains) use empty default constructors use direct variable access (not recommended, breaks OO) mix model with view (not recommended, breaks OO) use better algorithms remove redundant code optimize loops unroll loops use int as loop counter count/test loops towards 0 use Exception terminated loops for long loops use constants for expressions with known results, e.g. replace x = 3; . (x does not change) . ; x += 3; with x = 3; . (x does not change) . For Controversial Issues? ; x = 6; move code outside loops how to optimize: 1st check for how to, better algorithms, 2nd optimize loops use shift for *2 and thesis statements for controversial issues /2 do not initialize with default values (0, null) use char arrays for mutable Strings use arrays instead of collections use the private final modifier use System.arraycopy() to copy arrays use Hashtable keys with fast hashcode() do not use Strings as keys for scholarship application without, Hashtables use new Hashtable() instaed of Hashtable.clear() for very large Hashtables inspect JDK source use methods in order: static final instance interface synchronized use own specialized methods instead of statements issues, JDK's generalized ones avoid synchronization avoid new objects reuse objects use the original instead of overloaded constructors (give default parameters by your own) avoid inner classes use + for concenating 2 Strings, use Stringbuffer for concenating more Strings use clone to create new objects (instead of how to unit, new) use instance.hashcode() to test for equality of intances use native JDK implemented methods (as System.arraycopy()) avoid Exceptions (use Exceptions only for cases with probability 50%, else use error flags) combine multiple small try-catchs to one larger block use Streams instead of Readers, use Reader and Writer only if you need internationalization use buffering for issues, io use EOFException and ArrayOutOfBoundsException for essay on summer vacation for class 7, terminating io reading loops use transient fields to speedup serialisation use externalization instead of serialisation use multiple threads to increase perceived performance use awt instead of swing for issues, speed use swing instead of awt for in india, less memory use super.paint() to initially draw something (i.e. background) to increase perceived performance use your own wrapper for primitives (with setter methods) use Graphics.drawPolygon() (native implemented) instead of several Graphics.drawlines(). use low priority threads to initialize graphic components in the background use synchronized blocks instead of synchronized methods cache (SQL) Statements for DB access use PreparedStatements for DB access.
Accelerating GUI apps (after 1.4) (Page last updated March 2002, Added 2002-04-26, Author Dana Nourie, Publisher Sun). Tips: To add many items to a JComboBox, add them in one go using a Model on a vector, e.g. For Controversial? new JComboBox(new DefaultComboBoxModel(new Vector(allItemsInAnArray)));. This generates only one changed event. On Child Rights? Perform GUI operations in bulk to for controversial minimize the on summer vacation for class, events generated. Statements For Controversial? When initializing or totally replacing the write unit, contents of a model, construct a new one instead of reusing the existing one to minimize generated events. Use threads other then the GUI handling thread for long, indeterminate, or repetitive tasks.
VolatileImage allows you to create a hardware-accelerated offscreen image and manage the contents of that image. From 1.4 Swing double-buffers using VolatileImage hardware acceleration to thesis statements for controversial issues improve performance. How To Unit? Repaint small regions instead of entire sections or screens. For instance, when using tables, repaint a single table cell as needed instead of repainting the entire screen or table. Thesis Statements Issues? EventHandler provides support for dynamically generating event listeners that have a small footprint and can be saved automatically by the persistence scheme. MIDP tips (Page last updated March 2002, Added 2002-04-26, Author Eric Giguere, Publisher Sun). Tips: Make HTTP requests in a background thread. Essays? Use an asynchronous messaging model. Use WBXML to compress XML messages.
Article about avoiding creating objects where possible. (Page last updated 1996, Added 2000-10-23, Author Chuck McManis, Publisher JavaWorld). Tips: The mythology surrounding the slowness of thesis statements, garbage-collected systems is just that, myth. Of Christmas? I can show that the number of for controversial, instructions executed is the same whether I call malloc() and free() or I only essays of christmas, call malloc() and thesis for controversial issues some other code calls free(). Simple designs can easily run through many unnecessary objects, e.g. data wrapper objects like Integer. Of Christmas? Reuse objects where possible. Use -verbosegc to check the impact of garbage collection on your application. The Eight Fallacies of Distributed Computing (Page last updated 2000, Added 2002-03-25, Author Peter Deutsch, Publisher Sun). Tips: The network can fail to deliver at any time. Latency is significant. Bandwidth is always limited. Article on designing for performance focusing on interfaces (Page last updated January 2001, Added 2001-02-21, Author Brian Goetz, Publisher JavaWorld).
Tips: Avoid excessive object creation: be wary of object creation inside of tight loops when executing performance-critical code. Performance-conscious programmers avoid excessive use of String. Defining a utility class which is thesis statements issues, applied to data required by its constructor means that you must create a new object for of christmas, every piece of data to run it on. Thesis Statements Issues? Instead, do not require data in how to unit the constructor. Do not force methods to provide arguments with input in the form that is convenient rather than efficient. For example, don't require that arguments be passed only as String objects if a byte array or char array would also be functionally equivalent (try to support all formats, especially the efficient ones). Defining a method signature in terms of an interchange type (the type of object passed from a caller method to the callee method as an argument) reduces the interface's complexity while maintaining its flexibility, but sometimes this simplicity comes at for controversial issues the cost of essay for class 7, performance. HotSpot FAQ (Page last updated August 2000, Added 2001-02-21, Author ?, Publisher Sun). Tips: HotSpot has a bunch of startup options that may help you configure your VM to go faster.
HotSpot garbage collection parameters can be tuned with -Xincgc, -XX:NewSize, -XX:MaxNewSize and -XX:SurvivorRatio(and heap size parameters). Sun recommends you no longer use objects pools [this is rather a sweeping and thesis statements issues inappropriate statement. Object pools are still useful even with HotSpot, but presumably not as often as previously]. Undocumented option -Xconcurrentio may help performance when there are very many threads. It uses a lighter thread synchronization model. If using few threads, using -XX:+UseBoundThreads and of christmas the light weight process threads (LWP) library may improve performance. LWP threads are scheduled by thesis for controversial issues the JVM, system threads have kernel scheduling.
Don't call System.gc(). Warming loops is no longer necessary from HotSpot 2.0 (SDK 1.3). On Child Rights? HotSpot now supports on-stack-replacement. HotSpot supports -Xrunhprof options and statements for controversial issues also -Xaprof for object allocation statistics. Integer alignment of generated native code affects its speed [so it is conceivable that adding the odd bytecode could make code faster]. HotSpot can eliminate dead variables and on child in india dead code, i.e. variables that are assigned to but never used [in isolated code segments]. The generational-GC per thesis statements, object costs varies depending on application without the length of life of the object. A different HP tip page on optimizing Java performance, from the HP-UX Programmer's Guide for Java. Gives info on HP system performance monitoring too (Page last updated ?, Added 2000-10-23, Author ?, Publisher HP).
Tips: Maximize thread lifetimes and minimize thread creation/destruction cycles. Minimize contention for shared resources. Minimize creation of short-lived objects. Use -verbosegc to monitor garbage collection. Tune the applications to statements for controversial issues minimize the effects of garbage collections. Disk I/O should be minimized. Don't do random I/O to read a file serially (RandomAccessFile class). You should use buffered I/O. Complex AWT graphics will slow down your performance. Use the most current version of Java.
Use -mx and -ms to tune the heap size [now -Xms and -Xmx]. Profile the copy essay, code to find bottlenecks. Bill Venners on the right way to optimize (Page last updated May 1998, Added 2000-10-23, Author Bill Venners, Publisher Artima). Tips: Don't optimize until you know you have a problem. Measure the statements issues, program before and copy without after your optimization efforts. Profile the thesis for controversial issues, program to isolate the code that really matters to performance (10 to 20 percent), and essays critiquing just focus your optimization efforts there. Try to devise a better algorithm Use APIs in a smarter way Use standard code optimization techniques such as strength reduction, common sub-expression elimination, code motion, and loop unrolling. Only as a last resort should you sacrifice good object-oriented, thread-safe design and maintainable code in the name of thesis statements for controversial, performance.
Make methods static wherever possible. Avoid creating lots of short-lived objects. Application performance tuning (Page last updated July 2002, Added 2002-07-24, Author Baya Pavliashvili and Kevin Kline, Publisher informIT). Tips: Application performance problems can be caused and mitigated with any combination of the following areas: Network topology and throughput; Server hardware configuration; client application code; middle-tier components; database communication code; database configuration settings; logical and physical database design; operating system settings; client hardware; overall application architecture. Monitor the application.
Primary statistics worth analyzing are: the number of concurrent users; number of how to write, transactions per unit of time; duration of the longest and shortest transactions; and the average response time. Specify the performance targets. Consider using eye candy to distract attention during acceptable short waits. Identify which application tier contains the bottleneck and fix that. Thesis? It might be hardware or software; low-level or architecture. Prioritize which problems to fix according to the resources available. Object management article (Page last updated November 1999, Added 2000-12-20, Author Dennis M. How To Write? Sosnoski, Publisher JavaWorld). Statements Issues? Tips: Objects have a space overhead in addition to the space taken by the data held by the object.
Objects have a space overhead in addition to the space taken by the data held by the object. The overhead is on child rights, dependent on thesis for controversial issues the particular JVM, but there is always some. The space overhead is how to write, a per object value, so the thesis statements, percentage of scholarship without, overhead decreases with larger objects. If you work with large numbers of small objects, you can use a huge amount of memory simply for overhead. Different JVMs are optimized for short lived objects or for statements for controversial, long lived objects. How To? Object creation and garbage collection have significant overheads. Providing you're sensible about creating objects in heavily used code, it's easy to avoid the statements for controversial, object churn cycle. The easiest way to essay 7 reduce object creation in your programs is by statements using primitive types in place of objects.
Avoid using wrapper classes (for primitive data types, e.g. Integer) as they impose extra overheads. If you're working with a large number of primitive data types, you can avoid the excessive object overhead of wrappers by storing and passing values of the underlying primitive types, and essays only converting the values into the full objects when necessary for use with methods in the class libraries. Avoid convenience classes like Point if you can manage the thesis statements for controversial, underlying data directly. Reuse objects where possible.
Use object pools where this is on child rights, helpful in reusing objects, but be careful that the pool implementation does actually give a performance improvement (dedicated pools within the class can be significantly faster than abstract pool implementations). Implement pools so that the thesis statements issues, pool does not retain a reference to any allocated object, so that if the object is not returned to on child the pool, it can still be garbage collected when finished with (thus avoiding memory leaks). Website usability metrics (Page last updated May 2002, Added 2002-07-24, Author Sharon Gaudin, Publisher EarthWeb). Tips: A website must be easy to thesis for controversial navigate and have a quick display and without response time. Bad navigation metrics include: abandoned shopping carts; first time visitors look at one or two pages and disappear; dead ends require the back button; less than 5% buy something; any broken links. Statements? Good navigation metrics include: three pages or less from on summer vacation for class 7 wesbite entry to desired information; no streaming video or Flash introductions; multiple ways to reach the thesis statements, required information; up to date search engines; basic compancy and contact info one click away from the homepage. Common issues affecting Web performance (Page last updated June 2002, Added 2002-07-24, Author Drew Robb, Publisher EarthWeb).
Tips: Symptoms of network problems include slow response times, excessive database table scans, database deadlocks, pages not available, memory leaks and high CPU usage. Causes of performance problems can include the application design, incorrect database tuning, internal and external network bottlenecks, undersized or non-performing hardware or Web and application server configuration errors. On Child In India? Root causes of performance problems come equally from four main areas: databases, Web servers, application servers and the network, with each area typically causing about a quarter of the statements, problems. The most common database problems are insufficient indexing, fragmented databases, out-of-date statistics and faulty application design. Solutions include tuning the write, index, compacting the database, updating the database and rewriting the thesis statements issues, application so that the scholarship application essays, database server controls the query process. The most common network problems are undersized, misconfigured or incompatible routers, switches, firewalls and load balancers, and inadequate bandwidth somewhere along he communication route. The most common application server problems are poor cache management, unoptimized database queries, incorrect software configuration and poor concurrent handling of thesis statements for controversial, client requests. The most common web server problems are poor design algorithms, incorrect configurations, poorly written code, memory problems and overloaded CPUs. Having a testing environment that mirrors the expected real-world environment is very important in achieving good performance. The deployed system needs to be tested and continually monitored.
The smallest Hello World (Page last updated July 2002, Added 2002-07-24, Author Norman Richards, Publisher Java Developers Journal). Tips: [Brilliantly amusing search to make the smallest Hello World program.] Use the -g:none option to strip debugging bytes from classfiles. Most bytes in Java class files are from the constant pool, then the method declarations. The constant pool includes class and essay vacation for class method names as well as strings. The Java compiler will insert a default constructor if you don't specify one, but the constructor is only needed if you will create instances.
You can remove the constructor if you will not be creating instances. Statements For Controversial? Most variables and class references used by the code generate entries in the constant pool. Without? Reusing already existing constant pool entries for class/method/variable names reduces the thesis issues, class file size. Article on using smart proxies. (Page last updated November 2000, Added 2001-01-19, Author M. Jeff Wilson, Publisher JavaWorld). Tips: Use smart proxies to transparently cache data in the client, thus reducing the number of remote calls. Use smart proxies for caching frequently read, seldom-updated data of remote objects. Use smart proxies to monitor the essay for class, performance of RMI calls. Use smart proxies to prevent returning multiple copies of the same remote object to client code. Paper detailing the Best Practices for Developing High Performance Web and Enterprise Applications using IBM's WebSphere. All the thesis statements issues, tips are generally applicable to servlet/EJB development, as well as other types of server development. (Page last updated September 2000, Added 2001-01-19, Author Harvey W. Gunther, Publisher IBM). Tips: Do not store large object graphs in javax.servlet.http.HttpSession.
Servlets may need to write unit serialize and deserialize HttpSession objects for persistent sessions, and statements for controversial making them large produces a large serialization overhead. Use the tag %@ page session=false% to avoid creating HttpSessions in JSPs. Minimize synchronization in essay Servlets to avoid multiple execution threads becoming effectively single-threaded. Do not use javax.servlet.SingleThreadModel. Thesis Statements? Use JDBC connection pooling, release JDBC resources when done, and reuse datasources for JDBC connections. Use the HttpServlet Init method to perform expensive operations that need only be done once. Minimize use of System.out.println.
Avoid String concatenation +=. Access entity beans from session beans, not from essays article client or servlet code. Issues? Reuse EJB homes. Use Read-Only methods where appropriate in entity-beans to essays critiquing avoid unnecessary invocations to statements issues store. Use the lowest impact transaction level possible for each transaction. The EJB remote programming model always assumes EJB calls are remote, even where this is not so. Where calls are actually local to the same JVM, try to use calling mechanisms that avoid the remote call. Vacation For Class 7? Remove stateful session beans (and any other unneeded objects) when finished with, to avoid extra overheads in case the thesis statements, container needs to be passivated.
Beans.instantiate() incurs a filesystem check to create new bean instances. Use new to how to avoid this overhead. Tuning IBM's WebSphere product. White paper: Methodology for thesis for controversial, Production Performance Tuning. On Summer Vacation 7? Only non-product specific Java tips have been extracted here. (Page last updated September 2000, Added 2001-01-19, Author Gennaro (Jerry) Cuomo, Publisher IBM). Thesis Issues? Tips: A size restricted queue (closed queue) allows system resources to on child rights be more tightly managed than an open queue.
The network provides a front-end queue. Thesis For Controversial? A server should be configured to use the network queue as its bottleneck, i.e. only accept a request from the network when there are sufficient resources to process the request. This reduces the load on an app server. However, sufficient requests should be accepted to application essays ensure that the app server is working at thesis issues maximum capacity, i.e. try not to let a component sit idle while there are still requests that can be accepted even if other components are fully worked. Scholarship Application Essays? Try to thesis statements balance the workload of the various components. Essay? [Paper shows a nice throughput curve giving recommended scaling behavior for an server] The desirable target bottleneck is the CPU, i.e. a server should be tuned until the statements for controversial, CPU is the remaining bottleneck. Adding CPUs is a simple remedy to this. Use connection pools and cached prepared statements for database access. Object memory management is particularly important for server applications.
Typically garbage collection could take between 5% and 20% of the server execution time. Garbage collection statistics provide a useful monitor to determine the server's health. Use the verbosegc flag to collect basic GC statistics. GC statistcs to monitor are: total time spent in GC (target less than 15% of execution time); average time per GC; average memory collected per on summer for class, GC; average objects collected per GC. For long lived server processes it is particularly important to eliminate memory leaks (references retained to objects and never released). Thesis Statements Issues? Use -ms and -mx to tune the JVM heap. Bigger means more space but GC takes longer. Use the GC statistics to determine the critiquing article, optimal setting, i.e the setting which provides the minimum average overhead from GC. Statements? The ability to reload classes is typically achieved by testing a filesystem timestamp. This check should be done at on summer for class 7 set intermediate periods, and not on every request as the thesis statements, filesystem check is an expensive operation.
WebSphere V3 Performance Tuning Guide (Page last updated March 2000, Added 2001-01-19, Authors Ken Ueno, Tom Alcott, Jeff Carlson, Andrew Dunshea, Hajo Kitzh?fer, Yuko Hayakawa, Frank Mogus, Colin D. Wordsworth, Publisher IBM). Tips: [The Red book lists and essay on summer vacation discusses tuning parameters available to Websphere] Run an application server and any database servers on separate server machines. JVM heap size: -mx, -ms [-Xmx, -Xms]. Thesis Statements For Controversial Issues? As a starting point for a server based on a single JVM, consider setting the maximum heap size to 1/4 the total physical memory on the server and setting the minimum to 1/2 of the maximum heap. Of Christmas? Sun recommends that ms be set to somewhere between 1/10 and 1/4 of the mx setting. They do not recommend setting ms and mx to be the same. Bigger is not always better for heap size. In general increasing the size of the Java heap improves throughput to the point where the statements for controversial, heap no longer resides in physical memory. Once the heap begins swapping to disk, Java performance drastically suffers. Therefore, the mx heap setting should be set small enough to write contain the heap within physical memory. Also, large heaps can take several seconds to fill up, so garbage collection occurs less frequently which means that pause times due to statements for controversial GC will increase.
Use verbosegc to help determine the application without essays, optimum size that minimizes overall GC. Statements? In some cases turning off asynchronous garbage collection (-noasyncgc, not always available to all JVMs) can improve performance. Write Unit? Setting the JVM stack and native thread stack size (-oss and -ss) too large (e.g. greater than 2MB) can significantly degrade performance. When security is enabled (e.g. SSL, password authentication, security contexts and thesis access lists, encryption, etc) performance is degraded by significant amounts. Essays? One of the statements issues, most time-consuming procedures of a database application is establishing a connection to the database. Use connection pooling to minimize this overhead. Using a ternary search tree for fast searches of partial text matches (Page last updated February 2001, Added 2001-03-21, Author Wally Flint, Publisher JavaWorld).
Tips: [Article discusses several efficient algorthms for searching through ternary search trees which provide fast partial match searches of character array keys]. When synchronization is required (Page last updated July 2001, Added 2001-07-20, Author Brian Goetz, Publisher IBM). Tips: synchronization means mutual exclusion (if the same monitor is used), atomicity of the essays of christmas, synchronized block (again with respect to other threads using the same monitor) and synchronization of thread memory to main memory. Because synchronization synchronizes thread memory with main memory, there is a cost to synchronization beyond simply acquiring a lock. Too little synchronization can lead to corrupt data; too much can lead to reduced performance and deadlock. The costs of synchronization vary with JVMs, with more recent JVMs being more efficient. The costs of synchronization differs depending on for controversial whether or not threads are actually contending for locks (more expensive, slower), or for uncontended synchronization where the thread is basically acting in single-threaded mode (cheaper, faster). You need to synchronize or make volatile variables holding data that will be shared between threads. Composite operations may need synchronizing to scholarship application make them atomic even if each individual operation is already synchronized. Reducing thread contention (Page last updated September 2001, Added 2001-10-22, Author Brian Goetz, Publisher IBM). Tips: Thread contention impairs scalability because it forces the scheduler to serialize operations, even if a free processor is available.
Analyze your program to determine where contention is likely to occur. For Controversial Issues? Make synchronized blocks as short as possible. Spread synchronizations over without more than one lock. [Article provides a thread-safe hashed Map implementation with lower global contention than Hashtable.] If you will be acquiring and releasing the thesis, same lock many times (such as in a loop), acquire the lock before the loop: it is faster to acquire a lock that you already hold than one that nobody holds. J2EE worst practices (Page last updated April 2002, Added 2002-04-26, Author Brett McLaughlin, Publisher OnJava). Tips: The choice of data store type (RDB, ODB, XML-DB, directory-server, etc) affects performance, and should not be made without performance considerations. Article? Directory servers are optimized for frequent reads, with few writes. If you frequently add data to a directory server, performance degrades. Stateless session beans are soooo much faster. The hprof profiler (Page last updated December 2001, Added 2001-12-26, Author Bill Pierce, Publisher JavaWorld). Tips: Use the hprof profiler with the startup command java -Xrunhprof[:help][:suboption=value. ] MyMainClass. [Article describes using hprof and reading the resultant profile files to profile an application for memory leaks, cpu-bottlenecks and thread contention]. hprof can be used to profile object allocation (heap option), method bottlnecks (cpu option) and thread contention (monitor option). Weblogic tuning (generally applicable Java tips extracted) (Page last updated June 2000, Added 2001-03-21, Author BEA Systems, Publisher BEA).
Tips: Response time is affected by: contention and wait times, particularly for shared resources; and software and hardware component performance, i.e. the amount of time that resources are needed. Thesis For Controversial? A well-designed application can increase performance by simply adding more resources (for instance, an extra server). Copy Essay Without? Use clustered or multi-processing machines; use a JIT-enabled JVM; use Java 2 rather than JDK 1.1; Use -noclassgc. Use the maximum possible heap size that also is small enough to avoid the JVM from swapping (e.g. 80% of statements issues, RAM left over after other required processes). Consider starting with minimum initial heap size so that the thesis on child rights in india, garbage collector doesn't suddenly encounter a full heap with lots of garbage. Thesis Statements For Controversial Issues? Benchmarkers sometimes like to set the heap as high as possible to completely avoid GC for the duration of the benchmark. Distributing the application over several server JVMs means that GC impact will be spread in time, i.e. the various JVMs will most likely GC at different times from each. Copy Without? On Java 1.1 the most effective heap size is thesis for controversial issues, that which limits the how to write, longest GC incurred pause to statements for controversial the longest acceptable pause in essay on summer vacation processing time.
This will typically require a reduction in the maximum heap size. Too many threads causes too much context switching. Too few threads may underutilize the system. If n=number of threads, k=number of CPUs, then: (n k) by a moderate amount of threads is practically ideal; (n k) by many threads can lead to thesis for controversial significant performance degradation from context switching. Blocked threads count for less in the previous formulae. Symptoms of too few threads: CPU is waiting to do work, but there is work that could be done; Can not get 100% CPU; All threads are blocked [on i/o] and critiquing runnable when you do an execution snapshot. Symptoms of too many threads: An execution snapshot shows that there is a lot of context switching going on statements for controversial in your JVM; Your performance increases as you decrease the article, number of threads. If many client connections are dropped or refused, the TCP listen queue may be too short.
Try to avoid excessive cycling (creation/deletion or activation/passivation) of beans. Weblogic JDBC tuning (Page last updated April 1999, Added 2001-03-21, Author BEA Systems, Publisher BEA). Tips: Use connection pools to the database and reuse connections rather than repeatedly opening and thesis for controversial closing connections. Optimal pool size is when the connection pool is scholarship without, just large enough to service requests without waits. Thesis Statements? Cache frequently requested data in the JVM and avoid the unnecessary database requests. Speed up applet download and startup using zip/jar files containing just the classes needed for the applet. Essays Critiquing Article? Avoid accessing the database wherever possible. Fetch rows in thesis statements for controversial issues batches rather than one at a time, using the essays critiquing article, batch as a read-ahead mechanism (i.e. Statements? pre-fetch rows in batches).
Tune the batch size and the number of rows pre-fetched. Write Unit? Avoid pre-fetching BLOBs. Avoid moving data unless absolutely necessary. Process the data and produce results as close to its source as possible. Use stored procedures.
Streamline data before the result crosses the network. Use stored procedures to avoid extra network transfers. Use built-in DBMS set-based processing to thesis statements operate on multiple rows/tables in one request. Avoid row at a time processing, process multiple rows together wherever possible. Counting entries in without a table (e.g. using SELECT count(*) from myTable, yourTable where . ) is resource intensive. Try first selecting into temporary tables, returning only the count, and thesis statements then sending a refined second query to return only a subset of the rows in the temporary table.
Proper use of essays of christmas, SQL can reduce resource requirements. Use queries which return the minimum of data needed: avoid SELECT * queries. Issues? A complex query that returns a small subset of data is more efficient than a simple query that returns more data than is needed. Make your queries as smart as possible, i.e. as precise as possible to minimize the data transferred to just that subset that is required. Try to scholarship application without batch updates: collect statements together and execute them together in one transaction. Use conditional logic and temporary variables if necessary to for controversial issues achieve statement batching. Never let a DBMS transaction span user input.
Consider using optimistic locking. Optimistic locking employs timestamps to verify that data has not been changed by another user, otherwise the transaction fails. Essays Article? Use in-place updates, i.e. change data in rows/tables that already exist rather than adding or deleting rows/tables. Try to avoid moving rows or changing their sizes. Store operational data and historic data separately (or more generally store frequently used data separately from infrequently used data).
Keep your operational data set as small as possible, to statements issues avoid having to read through data that is irrelevant. DBMSs work well with parallelism. Try to design the scholarship without, application to do other things while interacting with the DBMS. Use pipelining and parallelism. Designing applications to support lots of parallel processes working on easily distinguished subsets of the work makes the application faster. If there are multiple steps to processing, try to design your application so that subsequent steps can start working on the portion of data that any prior process has finished, instead of thesis statements for controversial issues, having to wait until the prior process is write unit, complete. Choose the thesis statements for controversial issues, right driver for how to unit, your application, i.e. the fastest JDBC driver. JDBC optimizing for DB2 (Page last updated April 2002, Added 2002-04-26, Author John Goodson, Publisher WebSphere Developers Journal).
Tips: Use the same connection to issues execute multiple statements. Keep connection objects open, and reuse them, rather than repeatedly connecting and thesis on child rights in india disconnecting. Turn off autocommit, but don't leave transactions open for too long. Thesis? Avoid distributed transactions (transactions that span mutliple connections). Minimize the data retrieved from the thesis on child rights, database, both columns and rows. Thesis Issues? Use setMaxRows, setMaxFieldSize, and scholarship essays SetFetchSize. Use the most efficiently handled data type: character strings are faster than integers, which are in turn more efficient than floating-point and thesis timestamps. Use programmatic updates: updateXXX() calls on updatable resultsets. The resultset is already postioned at a row, so eliminating the usual overhead of finding the row to be updated when using an UPDATE statement. Cache any required metadata and use metadata methods as rarely as possible as they are quite slow.
Avoid using null parameters in metadata queries. Essay For Class? Use a dummy query to get the metadata for a column, rather than use the statements for controversial, getcolumns() Use parameter markers with stored procedures, rather than embedding data literally in the statement, to minimize parsing overheads. Essay For Class? Use prepared statements for repeatedly executing SQL statements Choose the optimal cursor: forward-only for sequential reads; insensitive for thesis statements issues, two-way scrolling. Copy Without? Avoid insenstive cursors for queries that only thesis statements for controversial issues, return one row. J2EE Performance tuning (Page last updated October 2001, Added 2001-10-22, Author James McGovern, Publisher Java Developers Journal).
Tips: Call HttpSession.invalidate() to essays critiquing clean up a session when you no longer need to thesis for controversial issues use it. For Web pages that don't require session tracking, save resources by application essays turning off automatic session creation using: %@ page session=false% Implement the HttpSessionBindingListener for all beans that are scoped as session interface and thesis issues explicitly release resources implementing the method valueUnbound(). Timeout sessions more quickly by setting the timeout or using session.setMaxInactiveInterval(). Essays Of Christmas? Keep-Alive may be extra overhead for dynamic sites. Use the include directive %@ include file=copyleft.html % where possible, as this is a compile-time directive (include action jsp:include page=copyleft.jsp / is a runtime directive). Use cache tagging where possible. Always access entity beans from session beans. For Controversial Issues? If only using an entity bean for copy, data access, use JDBC directly instead. Use read-only in the deployment descriptor. Cache access to EJB homes. Use local entity beans when beans are co-located in the same JVM.
Proprietary stubs can be used for caching and batching data. Use a dedicated remote object to generate unique primary keys. Follow standard JDBC optimizations: use connection pools; prefer stored procedures or direct SQL; use type 4 drivers; remove extra columns from the thesis for controversial, result set; use prepared statements when practical; have your DBA tune the article, query; choose the for controversial, appropriate transaction levels. Consider storing all database character data in Unicode to eliminate conversion overheads. But beware: this step will cause your database size to grow, as Unicode requires 2 bytes per character.
Use block fetches when the query will give a large ResultSet and all rows are needed. Use the Page-by-Page Iterator pattern when only copy essay, some of the rows may be needed. Consider using an thesis for controversial issues in-memory database (product) for data that doesn't need to be persisted. Write? Use an algorithm to prune caches to stop them growing too large. Performance is sometimes in perception: try to provide immediate feedback. Optimizing code is one of the last things developers should consider [after optimizing configurations, hardware, etc]. Using nonblocking I/O and statements for controversial memory-mapped buffers in SDK 1.4. (Page last updated September 2001, Added 2001-10-22, Author Michael T. Nygard, Publisher JavaWorld). Tips: Before SDK 1.4, servers had a number of how to write unit, performance problems: i/o could easily be blocked; garbage was easily generated when reading i/o; many threads are needed to scale the thesis statements issues, server. On Summer Vacation? Many threads each blocked on thesis statements i/o is an inefficient architecture in comparison to one thread blocked on many i/o calls (multiplexed i/o).
Truly high-performance applications must obsess about garbage collection. The more garbage generated, the lower the application throughput. Essays Of Christmas? A Buffer (java.nio.*Buffer) is a reusable portion of memory. Thesis Statements Issues? A MappedByteBuffer can map a portion of a file directly into memory. Direct Buffer objects can be read/written directly from Channels, but nondirect Buffer objects have a data copy performed for read/writes to i/o (and so are slower and may generate garbage). Convert nondirect Buffers to direct Buffers if they will be used more than once.
Scatter/gather operations allow i/o to operate to and from several Buffers in one operation, for increased efficiency. Where possible, scatter/gather operation are passed to even more efficient operating system functions. Channels can be configured to vacation operate blocking or non-blocking i/o. Using a MappedByteBuffer is more efficient than using BufferedInputStreams. The operating system can page into memory more efficiently than BufferedInputStream can do a block read. For Controversial? Use Selectors to essays multiplex i/o and for controversial avoid having to write unit block multiple threads waiting on i/o.
Combining apps in statements issues one JVM (Page last updated April 2002, Added 2002-04-26, Author Kirk Pepperdine, Publisher Java Developers Journal). Tips: Loading multiple applications in the same JVM allows resource sharing and reduce system memory requirements. Classloaders allow multiple applications to run in the same JVM without interfering with each other. [Article discusses the thesis on child rights, resource sharing problems of running multiple applications in the same JVM]. JDBC Drivers (Page last updated March 2002, Added 2002-04-26, Author Barrie Sosinsky, Publisher DevX). Tips: Type 1 drivers are JDBC-ODBC bridges, plus an ODBC driver. Recommended only for thesis for controversial, prototyping, not for production. Critiquing? Not suitable for high-transaction environments. Not well supported, and limited in functionality. Type 2 drivers use a native API, and are part-Java drivers.
Have a binary-code client loading overhead, and may not be fully-featured. Type 3 drivers are a pure Java driver which connects to database middleware. Can be server-based which is frequently faster than types 1 and 2. Thesis Statements Issues? Type 4 drivers are pure Java drivers for direct-to-database communications. This can minimize overheads, and generally provides the write unit, fastest driver. Thesis For Controversial? JDBC 3.0 has additional features to write improve performance such as advancements in connection pooling, statement pooling, RowSet objects. Opening a connection is the most resource-expensive step in database transactions. Statements Issues? Creating a connection requires multiple separate network roundtrips. Essays? However, once the thesis statements for controversial, connection object has been created, there is little penalty in leaving the connection object in place and reusing it for future connections. Connection pooling, keeps open a cache of database connection objects, making them available for scholarship without essays, immediate use. Statements For Controversial Issues? Instead of performing expensive network roundtrips to the database server to open a connection, a connection attempt results in the re-assignment of a connection from the local cache. RowSet objects are similar to scholarship application essays ResultSet objects, but can provide access to thesis for controversial database data while being disconnected.
This allows data to be efficiently cached in its simplest form. Prepared statement pooling (available from JDBC 3.0) caches SQL queries that have been previously optimized and run so that, should they be needed again, they do not have to go through optimization pre-processing again (avoiding optimization steps, such as checking syntax, validating addresses, and optimizing access paths and of christmas execution plans). Statement pooling can be a significant performance booster. Statement pooling and connection pooling in for controversial JDBC 3.0 can cooperate to share statement pools, so that connections that can use a cached statement from another connection, thus incurring statement preparation overheads only once on the first execution of some SQL by any connection. Critiquing? Database drivers developed by vendors other than the the database vendor can be better performing and more feature full. (Driver vendors concentrate on the driver, database vendors have many other things to consider). Statements For Controversial? Type 3 and type 4 third-party drivers can provide better performance than the database vendor's native-API (type 2) driver. Try to thesis rights in india use a driver that supports JDBC 3.0 as it includes support for performance enhancing features including DataSource objects, connection pooling, distributed transaction support, RowSets, and prepared statement pooling. Type 3 and Type 4 drivers are the drivers to use when performance is important. Shortened version of chapter 2, I/O, from Early Adopter J2SE 1.4 (Page last updated October 2001, Added 2001-10-22, Author James Hart, Publisher Sun). Tips: Non-blocking I/O can improve performance by minimizing the amount of time spent in statements for controversial issues I/O calls, though they may add complexity to the application. The old I/O classes can now be interrupted more reliably from 1.4.
FileChannel.transferFrom() is an efficient way to copy data between files. Shortened version of chapter 5, Utilities: The Logging Architecture, from Early Adopter J2SE 1.4 (Page last updated October 2001, Added 2001-10-22, Author James Hart, Publisher Sun). Tips: Logging can take place asynchronously: a call to log can return before the log has been formatted and written. For Class 7? The logging framework provides methods (in Logger) for recording method activity, but this may have a large overhead to issues use. Coding standards with a small but interesting section (section 7.3) on essays critiquing article optimizations (Page last updated January 2000, Added 2001-04-20, Author Scott Ambler, Publisher AmbySoft). Tips: Optimizing code is one of the last things that programmers should be thinking about, not one of the first. Don't optimize code that already runs fast enough. Prioritize where speed comes among the following factors, so that goals are better defined: speed, size, robustness, safety, testability, maintainability, simplicity, reusability, and portability.
The most important factors in looking for for controversial issues, code to essays article optimize are fixed overhead and performance on large inputs: fixed overhead dominates speed for small inputs and the algorithm dominates for large inputs (a program that works well for both small and large inputs will likely work well for medium-sized inputs). Operations that take a particular amount of time, such as the way that memory and buffers are handled, often show substantial time variations between platforms. Users are sensitive to thesis particular delays: users will likely be happier with a screen that draws itself immediately and then takes eight seconds to load data than with a screen that draws itself after taking five seconds to load data. Give users immediate feedback: you do not always need to make your code run faster to optimize it in essay without the eyes of thesis statements for controversial, your users. Slow software that works is almost always preferable to fast software that does not. Overview of common application servers. (Announced at http://www.theserverside.com/home/thread.jsp?thread_id=9581). I've extracted the performance related features (Page last updated October 2001, Added 2001-10-22, Author Pieter Van Gorp, Publisher Van Gorp). Tips: Load balancing: random; minimum load; round-robin; weighted round-robin; performance-based; load-based; dynamic algorithm based; dynamic registration. Clustering. Additionally: distributed transaction management; in-memory replication of session state information; no single point of failure. Connection pooling.
Caching. On Summer? JNDI caching. Thesis? Distributed caching with synchronization. Thread pooling. Configurable user Quality of copy essay without, Service. Analysis tools. Statements Issues? Low system/memory requirements. Optimized subsystems (RMI, JMS, JDBC drivers, JSP tags cacheable page fragments). Essay On Summer For Class 7? Optimistic transaction support. Atomic File Transactions. (Page last updated November 2001, Added 2001-11-27, Author Jonathan Amsterdam, Publisher OnJava). Tips: If you don't require powerful search capabilities, using flat files may be faster than dealing with a database.
Basic file operations (deletion, creation, renaming) are atomic. Other operations and combinations of operations are not atomic. Atomicity can be built but comes at a performance cost. You will have to determine whether the increase in statements robustness is of christmas, worth the slowdown in thesis for controversial issues your application. Do the I/O in a background thread to mitigate the performance impact of adding atomicity to scholarship application file transactions. [Article discusses how to use a free package which provides atomicity for file transactions, and how the atomicity is statements issues, provided]. Atomic File Transactions, Part 2 (Page last updated February 2002, Added 2002-02-22, Author Jonathan Amsterdam, Publisher OnJava). Tips: [Article continues implementation of of christmas, a framework for atomic file transactions].
If a transaction creates a file and issues then performs several other actions on it, there is no need to undo the actions -- it is enough to delete the how to write, file. If a backup copy of a file is issues, made, then it is unnecessary to roll back all subsequent actions on the file: recovery can simply restore the application without, backup. MIDP memory tuning (Page last updated June 2002, Added 2002-07-24, Author Jonathan Knudsen, Publisher Sun). Tips: Use an obfuscator to minimize the size of classes. Minimize resource sizes by statements for controversial issues using as few images as possible, and scholarship using fewer colors in the images you do use.
Use as few objects as possible. Dereference objects (set them to null) when they're no longer useful so they will be garbage-collected. Statements For Controversial Issues? Catch OutOfMemoryErrors on all allocations, or at least the large ones. Write Unit? Don't let an OutOfMemoryError take your application by surprise. MIDlets use three types of memory: program memory, heap, and persistent storage. Each of issues, these may be scarce and they should all be treated with respect. Design patterns catalog (Page last updated 2001, Added 2002-01-25, Author ?, Publisher Sun). Tips: [Page lists some patterns with summaries and links to detailed info.
Patterns are: Data Access Object; Fast-Lane Reader; Front Controller; Page-by-Page Iterator; Session Facade; Value Object]. Use the Data Access Object pattern to essay on summer vacation for class 7 decouple business logic from data access logic, allowing for optimizations to for controversial issues be made in how data is managed. Use the Fast-Lane Reader pattern to accelerate read-only data access by not using enterprise beans. Use the Front Controller pattern to centralize incoming client requests, allowing optimizations to be made in aggregating the resulting view. Use the Page-by-Page Iterator pattern to efficiently access a large, remote list by retrieving its elements one sublist of value objects at write a time. Use the Session Facade pattern to provide a unified, workflow-oriented interface to statements a set of enterprise beans, thus minimizing client calls to essay on summer vacation for class server EJBs. Use the Value Object pattern to efficiently transfer remote, fine-grained data by sending a coarse-grained view of the data. EJB design (Page last updated January 2002, Added 2002-01-25, Author Boris Lublinsky, Publisher Java Developers Journal). Tips: Some application server implementations (e.g., WebSphere) automatically convert remote communications to issues local communications to make them faster. Write Unit? Low granularity (i.e. fine-grained) methods in an EJB typically leads to thesis statements poor performance of the overall system. Local interfaces in EJB 2.0 is one attempt to improve overall performance: local interfaces provide for beans in the same container to interact locally without involving RMI.
The most effective way to of christmas improve the overall performance of thesis statements for controversial, EJB-based applications is to minimize the amount of method invocations, making the communications overhead negligible compared with the execution time. This can be achieved by implementing coarse-grained methods. Copy? Entity beans should not be simply mapped to database tables. Treating entity beans as such fine-grained objects which are effectively wrappers on table rows leads to increased network communications and thesis statements issues heavier database communications than if entity beans are treated as coarse-grained components. For optimal performance, entity beans should be designed to: have large granularity, which usually means they should contain multiple Java classes and support multiple database tables; be associated with a certain amount of persistent data, typically multiple database tables, one of which should define the critiquing, primary key for the whole bean; support meaningful business methods and encapsulate business rules to statements for controversial issues access the data. Don't use client transactions in the EJB environment since long-running transactions that can cause database lockup. Entity beans are transactional resources due to their stateful nature, but application server vendors often rely on the underlying database to lock and resolve access appropriately. Essay On Summer For Class 7? Although this approach greatly improves performance, it provides the potential for statements for controversial issues, database lockup. Design Patterns (Page last updated January 2002, Added 2002-01-25, Author Vijay Ramachandran, Publisher Sun). Tips: [Article discusses several design patterns: Model-View-Controller, Front Controller, Session Facade, Data Access Object].
Use the Front Controller pattern to rights channel all client requests through a single decision point, which allows the application to for controversial issues be balanced at unit runtime. Use a Session Facade to for controversial issues provide a simple interface to a complex subsystem of enterprise beans, and to reduce network communication requirements. Use Data Access Objects to essay on summer decouple the business logic from the data access logic, allowing data access optimizations to thesis for controversial issues be decoupled from other types of optimizations. J2EE Design Patterns for the presentation tier (Page last updated January 2002, Added 2002-01-25, Author Sue Spielman, Publisher OnJava). Tips: [Article discusses several design patterns: Intercepting Filter, Front Controller, View Helper, Composite View, Service To Worker, Dispatch View. Performance is not explicitly covered, but at least a couple are relevant to getting good performance]. Thread programming (Page last updated January 2002, Added 2002-01-25, Author Karthik Rangaraju, Publisher DevX).
Tips: Use Djikstra semaphores (synchronized acquire()/release()) to control access to a finite pool of resources. How To? Conditional events provide a more sophisticated version of the wait()/notify() mechanism which avoids some potential problems of thesis issues, that mechanism. Blocking queues provides a mechanism for vacation, reliably distributing requests to multiple server threads. A dispatcher-worker model consists of a dispatcher which hands requests of to multiple worker threads. A pipeline model consists of a dispatcher which iteratively hands a particular request to one worker thread after another, with each worker thread completing part of the overall request. Some (Intel chip) optimization myths debunked. (Page last updated March 2002, Added 2002-04-26, Author George Walsh, Publisher DevX). Statements? Tips: If optimization and essays performance tools are used throughout development rather than tacked on at the end as a final optimization phase, time to market and thesis statements for controversial costs can actually be decreased by speeding up the process of thesis rights in india, locating problems and bottlenecks in code.
Not taking advantage of new optimized interfaces will ultimately put you at a competitive disadvantage. Double-checked locking revisited. (Page last updated November 2001, Added 2001-11-27, Author Brian Goetz, Publisher JavaWorld). Tips: Double-checked locking is not guaranteed to produce consistent results. Using a ThreadLocal in the double-checked locking test is guaranteed to produce consistent results, but is slower than avoiding double-checked locking altogether. Statements? ThreadLocal is faster in essay vacation each SDK release through 1.2, 1.3 and 1.4.
1.4 ThreadLocal may be fast enough to provide an efficient double-checked locking test. Command objects for RMI. (Page last updated October 2001, Added 2001-11-27, Author William Grosso, Publisher OnJava). Tips: Use Command objects to thesis statements issues automatically queue or retry RMI calls. Caching RMI stubs. (Page last updated October 2001, Added 2001-11-27, Author William Grosso, Publisher OnJava). Tips: Remote method calls are much slower than local calls, at least 1000 times slower. Reduce the number of remote calls made by an application to improve performance. Cache remote objects locally where possible, rather than repeatedly fetching them. Write Unit? Use Command objects to transparently add a remote stub cache to an RMI application. Caching stubs keeps them from being garbage collected, and may prevent an RMI server from closing. Use a policy to expire stubs and delete them from the cache. Website performance. (Page last updated October 2001, Added 2001-11-27, Author Gordon Benett, Publisher Intranet Journal).
Tips: Some e-commerce consultants cite an attention span on the order of eight seconds as the threshold for statements, abandoning a slow retail site. Where broadband connections are the norm, pages that don't appear instantly stand a good chance of never being seen: slow pages might as well be no pages. Systems can only be designed to essays meet performance goals if those goals have been identified. Thesis Statements For Controversial Issues? Determine what range of response times will be acceptable. Try to understand the performance impacts of scholarship without, your design decisions. However the statements for controversial issues, performance of some design choices can be hard to predict and essays may remain unclear before testing. Test the thesis statements issues, system under conditions that simulate real patterns of use. Intermittent hard to repeat performance problems are not worth addressing unless they are in a business critical part of the website which provides corporate revenue.
Use a rapid, iterative development process in combination with frequent performance testing. Try to plan up-front rather than have to rely on late-phase tuning. High performance graphics (Page last updated February 2002, Added 2002-03-25, Author ?, Publisher Sun). Thesis On Child Rights? Tips: The large number extra features and increased cross-platform compatibility added to the Java Graphics framework in SDK 1.2 made the graphics slower than the statements, 1.1 Graphics. SDK 1.4 targeted these performance issues head on. Essay On Summer? VolatileImage allows you to create hardware-accelerated offscreen images, resulting in thesis for controversial issues better performance of Swing and gaming applications in particular and essay 7 faster offscreen rendering. When filling a shape with a complex paint, Java 2D must query the Paint object every time it needs to assign a color to a pixel whereas a simple color fill only requires iterating through the pixels and assigning the same color to all of them. The graphics pipeline (from SDK 1.4) only gets invalidated when an thesis statements issues attribute is changed to essays of christmas a different type of value, rather than when an attribute is statements for controversial issues, changed to a different value of the same type. Copy? For example rendering one opaque color is the same rendering another opaque color, so this would not invalidate the pipeline. But changing an opaque color to a transparent color would invalidate the pipeline.
Smaller font is rendered faster than larger font. Hardware-accelerated scaling is currently (1.4.0 release) disabled on Win32 because of quality problems, but you can enable it with a runtime flag, -Dsun.java2d.ddscale=true. From SDK 1.4 many operations that were previously slow have been accelerated, and produce fewer intermediate temporary objects (garbage). Statements For Controversial? Alpha blending and anti aliasing adversely affect performance. Only opaque images or images with 1-bit transparency can be hardware accelerated currently (1.4.0). Essays Of Christmas? Use 1-bit transparency to make the thesis statements issues, background color of a sprite rectangle transparent so that the character rendered in the sprite appears to move through the landscape of your game, rather than within the sprite box. Create images with the same depth and type of the screen to avoid pixel format conversions. Essay On Summer 7? Use either Component.createImage() or GraphicsConfiguration.createCompatibleImage(), or use a BufferedImage created with the ColorModel of the for controversial, screen.
Rectangular fills--including horizontal and vertical lines--tend to of christmas perform better than arbitrary or non-rectangular shapes whether they are rendered in statements issues software or with hardware acceleration. If your application must repeatedly render non-rectangular shapes, draw the shapes into 1-bit transparency images and copy the images as needed. If you experience low frame rates, try commenting out pieces of your code to find the copy without, particular operations that are causing problems, and replace these problem operations with something that might perform better. Various flags are available that affect performance, but may affect quality in some environments. These include: NO_J2D_DGA (no Solaris hardware acceleration); USE_DGA_PIXMAPS (use Solaris DGA acceleration of pixmaps); -Dsun.java2d.noddraw=true (turn off DirectDraw); -Dsun.java2d.ddoffscreen=false (disable DirectDraw offscreen acceleration); -Dsun.java2d.ddscale=true (enable hardware acceleration in Win32); -Dsun.java2d.pmoffscreen=true/false (store images in pixmaps under Unix); You can trace graphics performance using the statements for controversial, flag -Dsun.java2d.trace=optionname,optionname. where the essays, options are log (print primitives on execution); timestamp (timestamp log entries); count (print total calls of each primitive used); out:filename (send logs to filename); verbose (whatever); help (help); Assertions (Page last updated April 2002, Added 2002-04-26, Author Glen McCluskey, Publisher Sun). Tips: Disabled assertions add a cost of one check of a global state flag Enabled assertions add a cost of a check of a global state flag and thesis issues evaluating the essays article, boolean expression. Also the cost of thesis for controversial, throwing a new exception is added if the assertion fails. Use the conditional compilation idiom applied to assertions to remove assertions completely from the bytecode.
GC performance tuning (Page last updated February 2002, Added 2002-03-25, Author Alka Gupta and Michael Doyle, Publisher Sun). Tips: The point when garbage collection kicks in is out of the control of the application. This can cause a sequential overhead on the application, as the copy essay, garbage collector suspends all application threads when it runs, causing inconsistent and thesis statements unacceptable application pauses, leading to high latency and application without decreased application efficiency. For Controversial? verbosegc provides detailed logs of the garbage collector activities The live transient memory footprint of an application is the (Garbage generated per call) * (duration of the call) * (number of calls per second) . GC pause time caused by two-space collection of short-lived objects is directly proportional to the size of the memory space allocated to holding short-lived objects. But smaller available space can mean more frequent GCs. Higher frequency GC of short-lived objects can inadvertently promote short-lived objects to old space where longer lived objects reside [because if the the object is in short-lived object area for several GCs, then GC decides it's long-lived.] The promoteAll option will force the GC to assume that any object surviving GC of essay without, young space is for controversial issues, long-lived, and is immediately promoted to old space.. The short-lived object space needs to be configured so that GC pause time is not too high, but GCs are not run so often that many short-lived objects are considered long-lived and so promoted to the more expensively GCed long-lived object space.
The long-lived object space needs to be large enough to avoid an out-of-memory error, but not so high that a full GC of old space pauses the essay for class 7, JVM for too long. [Article covers 1.2 and 1.3 GC memory space models]. A significant GC value to focus on is the GC sequential overhead, which is the the percentage of the system time during which GC is running and application threads are suspended: (Sequential GC pause time added together) * (100) / (Total Application run time) . The concurrent garbage collector runs only thesis for controversial, most of the old space GC concurrently. Some of the old space GC and all the young space GC is sequential. GC activity can take hours to settle down to its final pattern. Fragmentation of old space can cause GC times to copy degrade, and thesis statements for controversial issues it may take a long time for the old space to become sufficiently fragmented to show this behavior. GC options can reduce fragmentation (such as bestFitFirst). The promoteAll option produced a significant improvement in write unit performance [which I find curious]. Minimizing bytecode size for thesis statements for controversial, J2ME (Page last updated February 2002, Added 2002-03-25, Author Eric Giguere, Publisher Sun). Tips: Eliminate unnecessary features. Avoid inner classes: make the critiquing article, main class implement the required Listener interfaces and thesis handle the callbacks there.
Use built-in classes if functionality is close enough, and of christmas work around their limitations. Collapse inheritence hierarchies, even if this means duplicating code. Thesis Statements For Controversial? Shorten all names (packages, classes, methods, data variables). Some obfuscators can do this automatically. Thesis On Child Rights In India? MIDP applications are completely self-contained, so you can use the default package with no possible name-clash. Thesis Statements For Controversial Issues? Convert array initialization from code to extract data from a binary string or data file. Array initialization generates many bytecodes as each element is separately initialized.
Sun engineering report on performance tests of on summer, various configurations of the 1.2.2 and 1.3 JVM (Page last updated February 2001, Added 2001-02-21, Author Ed Ort, Publisher Sun). Tips: Different versions of the Sun JVM support different optimization flags. Some flags may allow you to configure the garbage collector generational spaces. Configure heap space using -Xms and -Xmx [-ms and -mx for statements issues, 1.1.x JVMs] to optimize the scholarship essays, JVM heap memory for improved performance. If the JVM supports configuring the garbage collector generational spaces (-Xgenconfig in 1.2.2; -XX:newSize, -XX:MaxNewSize, -XX:SurvivorRatio in 1.3), then you can improve performance by specifying generation spaces more appropriate for statements for controversial, your application [you can start with some appropriate configuration depending on the ratios of short-lived to medium-lived to long-lived objects, then test multiple configurations to rights determine the optimal config]. The 1.3 JVM appears to be faster when run with the thesis statements for controversial issues, -server flag. The -Xoptimize flag seems to improve performance on how to write unit those 1.2.x JVMs that support it. Discussion on JDBC performance (Page last updated August 2000, Added 2001-02-21, Author , Publisher JGuru). Tips: Use a connection pool mechanism whenever possible. Use prepared statements.
Use stored procedures. Select only thesis statements for controversial issues, required columns rather than using select * from Table xyz. Always close Statement and of christmas ResultSet objects as soon as possible. Thesis Statements Issues? Work with DatabaseMetaData to get information about scholarship essays, database functionality. Statements Issues? Always catch and handle database warnings and critiquing exceptions.
Time DB queries. Use the most appropriate datatype specific kinds of data, e.g. store dates as a date type rather than varchar. Use scrollable ResultSet (JDBC 2.0). Stay away from the JDBC-ODBC and thesis issues other Type 1 drivers where possible. Improving J2EE performance (Page last updated May 2002, Added 2002-07-24, Author Scott Marlow, Publisher The Server Side). Tips: Set performance goals before development starts. If supporting clients with slow connections, consider compressing data for network communication. Copy Essay? Minimize the number of network round trips required by the application.
For applications to scale to many users, minimize the amount of shared memory that requires updating. Cache data to minimize lookup time, though this can reduce scalability if locks are required to access the cache. If there are more accesses than updates to a cache, share the access lock amongst all the accessors, though be aware that this reduces the window for updators to thesis statements issues lock the cache. For optimum performance, zero shared memory provides a cache per user. Be methodical to ensure that changes for scholarship application essays, performance do actually improve performance. Eliminate memory leaks before tuning execution speed. Use a test environment that correctly simulates the expected deployment environment.
Simulate the expected client activity, and compare the performance against your expected goals. Consider which metrics to issues measure, such as: Max response time under heavy load; CPU utilization under heavy load; How the application scales as additional users are added. Profile the on child rights in india, application to find the bottlenecks. Correct bottlenecks by making one change at a time and testing for improvement. Generate stack traces to look for bottlenecks which are multi-thread conflicts (waiting for for controversial issues, locks). How To? Improving the performance of a method that is thesis for controversial, called 1000 times and takes a tenth of a second on average each call, is essays of christmas, better than improving the performance of a method that is thesis statements for controversial, only called 10 times but takes 1 second each call.
Don?t cache data unless you know how and when to essay on summer for class invalidate the cached entries. An assortment of thesis, tips (Page last updated 2000, Added 2000-10-23, Author Curt Smith, Publisher Smith). Essay Without? Tips: Use the Java compiler?s optimization flag (javac -O) Profile the statements for controversial issues, application (using -prof) re-code the methods that are taking the longest. Avoid repeatedly instantiating exceptions. Thesis On Child? Reuse exceptions in for controversial preference. Copy Without? Move common subexpressions to one execution. Eliminate casts, or reduce the number of casts being made.
Method local variables are faster than Class variables Declare method arguments final if they are not modified in thesis statements for controversial issues the method. In general declare all variables final if they are not modified after being initialized or set to some value. How To? Declare methods private and/or final whenever that makes sense. This can help the compiler inline methods. [final methods are of dubious value] Buffer i/o. Use BufferedReaders.
DON?T create static strings via new(). Use String.intern() to reduce the for controversial, number of strings in your runtime. [but this is an essay without expensive operation] Use char arrays for all character processing in loops, rather than using the String or StringBuffer classes. StringBuffer default size is 16 chars. Set this to the maximum expected string length. StringTokenizer is inefficient. It can be optimized by storing the string and delimiter in a character array instead of in a String, or by storing the highest delimiter character to allow a quicker check. Accessing arrays is much faster than accessing vectors, String, and StringBuffer. Use System.arraycopy() to improve performance.
Initialize expensive arrays in class static initializers, and create a per instance copy of this array initialized with System.arrarycopy(). Vector is convenient to statements for controversial issues use, but inefficient. For best performance, use it only when the structure size is unknown, and efficiency is not a concern. Application Essays? When using Vector, ensure that elementAt() is not used inside a loop. Vector element access is thesis statements for controversial, faster using a subclassed non-synchronized accessor. Re-use Vectors by using Vector.removeAllElements().
Initialize Vector to the maximum expected size. Re-use Hashtables by using Hashtable.clear(). How To Write Unit? Set the Hashtable size to be large enough to hold the expected elements. Use a prime number for table size. Override hashcode() methods of Hashtable keys to improve hashing efficiency. Use non-synchronized hash table classes. Increase heap size to reduce garbage collection [actally to defer it - this is thesis issues, a balancing act]. Use the -verbosegc option to monitor garbage collection.
Use arrays of smaller datatypes (short rather than int) is possible. Avoid allocating objects in essay loops (readLine() is a common example). Minimizing synchronization may take work, but can pay off well. Thesis Statements? Polling is only acceptable when waiting for outside events and should be performed in a side thread. Application Without Essays? Use wait/notify instead. Statements For Controversial Issues? Eliminate calls to vacation for class synchronized methods (but be careful of being overly ambitious in this).
It is slightly faster to call a synchronized method than to enter a synchronized block. Calling a synchronized method when the monitor is already owned by the thread executes somewhat faster than calling a synchronized method when the monitor isn't already owned by the thread. Creating objects is expensive. Consider reusing objects in reuse pools. Move new(), invariants and thesis constant conditionals outside of loops. Unroll loops.
Make tests in loops as simple as possible. Loop tests run backwards are slightly faster [actually the test comparing to 0 is scholarship without, what is faster]. Thesis Statements? Use local variables, rather than any other type of critiquing article, variable, in loops. Combine similar loops. Nest the busiest loop, if loops are interchangeable. Convert expressions to table lookups [doesn't always work]. For Controversial Issues? Cache values that are expensive to fetch or compute. Pre-compute results. Delay computation of results until they are needed [if the on summer for class 7, computation comes at statements for controversial a bad time] Put all one-time initializations into a class initializer. Various performance tips (Page last updated May 2001, Added 2001-06-18, Author Asha Balasubramanyan, Publisher Nandighosha). Tips: Use buffered I/O.
Use stream I/O rather than character I/O (Readers/Writers) if you are dealing with only for class, ASCII characters. Avoid premature flushing of buffers. Recycle objects. try to minimize the number of thesis statements for controversial issues, objects you create in your java programs. Essay? Factor out constant computations from loops. Push one-time computations into methods called once only.
Use StringBuffer when dealing with mutable strings. Initialize the StringBuffer with the proper size. Thesis Statements For Controversial Issues? Comparison of two string objects is faster if they differ in length. Avoid converting Strings to bytes and back. StringTokenizer is slow.
Write your own tokenizer. Essay On Summer 7? Use charAt() instead of StartsWith() in case you are looking for a single character within a String. Avoid premature object creation. Thesis Statements For Controversial Issues? Creation should be as close to the actual place of use as possible. Avoid initializing twice. Zeroing buffer contents is not usually required. Be careful about the order of evaluation of expressions with OR and article AND conditions. Use ArrayList for non-synchronized Vectors.
Minimize JNI calls in your code. Minimize calls to Date and related classes. Avoiding synchronization deadlocks (Page last updated October 2001, Added 2001-10-22, Author Brain Goetz, Publisher JavaWorld). Tips: Deadlocks are difficult to identify from code analysis, and can occur unexpectedly. Statements For Controversial? Always acquire locks in the same order to avoid one common cause of deadlocking. Rights In India? If you can guarantee that all locks will always be acquired in a consistent order, then your program will not deadlock. Try to avoid acquiring more than one lock at a time (though this is for controversial issues, usually impractical). Keep synchronized blocks of code as short as possible.
Counting object creation (Page last updated December 2001, Added 2002-02-22, Author Heinz M. Kabutz, Publisher Kabutz). Tips: Add a counter in to the Object constructor to trace object creation. Doesn't trace arrays [nor objects created from deserialization]. Performance tuning (Page last updated September 2001, Added 2001-10-22, Author James McGovern, Publisher Java Developers Journal). Tips: Often there's a trade-off between designing for reuse and designing for performance. Performance generally wins: customers understand fast-performing systems when they don't necessarily understand code reuse. Exceptions degrade performance and should be used for error conditions only, not control flow. Don't initialize variables twice: Java by default initializes variables to a known value. Use the write, factory pattern to enable reuse or cloning of objects. Make classes final. Use local variables as much as possible.
Use non-blocking I/O (available from 1.4, or use www.cs.berkeley.edu/ mdw/proj/java-nbio/download.html for earlier versions). Create/Use method interfaces that reduce overhead. Use bit-shifting instead of multiplication or division by thesis for controversial issues powers of application without essays, two. Choose the JVM that runs your application fastest. Use clustering application servers. Avoid stateful sessions. Profile and tune the application (architecture and thesis statements for controversial issues code).
Set aside at least 20% of the total project time for performance. Copy Essay Without? Make sure your QA environment mirrors your production environment, and your QA procedure tests the application at statements for controversial different loads, including a low and fully scaled loads. Why CMP is better than BMP (Page last updated April 2002, Added 2002-04-26, Author Tyler Jewell, Publisher Weblogic Developers Journal). Tips: Use CMP except in specific cases when BMP is unit, necessary: fields use stored procedures; persistence is thesis statements issues, not simple JDBC (e.g. JDO); One bean maps to multiple tables; non-standard SQL is used. CMP can make many optimizations: optimal locking; optimistic transactions; efficient lazy loading; efficiently combining multiple queries to the same table (i.e. On Child Rights? multiple beans of the same type can be handled together); optimized multi-row deletion to handle deletion of beans and thesis statements issues their dependents. Scalable recoverable applications (Page last updated May 2002, Added 2002-07-24, Author Billy Newport, Publisher The Server Side). Tips: [Article describes several approaches to building a scalable recoverable system] Split the application into a transactional part and a non-transactional part. The non-transactional part can be replicated. Using a single machine limits both reliability and scalability.
Scalability is completely dependent on how powerful the single machine can become. Multiple front-end machines with http request load balancing is more reliable, but the database machine is still a single point of failure. A database caching layer in the servlet helps performance. Copy? An EJB caching layer is difficult to statements for controversial issues achieve. Oracle 9i includes queryable snapshots of the main database which can offload the write unit, query to run against statements for controversial issues the clients local snapshot. Write Unit? An in-memory database (such as TimesTen) is very, very fast and issues can act as a queryable cache for a back end database. Database instances on each machine, with replication increases reliability and scholarship application essays access speed.
But updates now need to thesis statements be handled differently. Alternatives include: buffering updates; using message queues; database update replication. Partitioning the unit, database across multiple machines adds scalability, but must be done with care. If you want very reliable systems then everything has to thesis statements for controversial be controlled. A load balancing message queue may be needed for a high rate of messages (500/sec). Note that reliable systems should ensure that all duplicated data have no single points of failure in the software or hardware chain behind the data (different controllers, UPSs, etc). Techniques to application without avoid deadlocks (Page last updated September 2001, Added 2001-10-22, Author Mark Dykstra, Publisher Java Developers Journal). Thesis? Tips: Potential deadlocks can be caused by coding styles. Always acquire a set of locks in essay the same set order.
Don't hold a lock and wait for thesis statements for controversial issues, an event. Specify which thread should have access to data at any time. Ensure that both access and update to on summer for class 7 the same variable is synchronized on the same monitor. Stateful to Stateless Bean (Page last updated February 2002, Added 2002-03-25, Author Brett McLaughlin, Publisher OnJava). Tips: Stateless session beans are much more efficient than stateful session beans.
Stateless session bean have no state. Most containers have pools of stateless beans. Each stateless bean instance can serve multiplw clients, so the statements for controversial issues, bean pool can be kept small, and doesn't need to thesis rights change in size avoiding the main pooling overheads. A separate stateful bean instance must exist for statements issues, every client, making bean pools larger and more variable in article size. Thesis For Controversial Issues? [Article discusses how to move a stateful bean implementation to stateless bean implementtaion]. Alternatives to copy using 'new'. (Page last updated March 2002, Added 2002-03-25, Author Jonathan Amsterdam, Publisher Dr. Dobb's). Tips: The 'new' operator is not object oriented, and prevents proper polymorphic object creation. Constructors must be made non-public and statements for controversial preferably private to write unit limit the number of objects of thesis, a class. The Singleton pattern and of christmas the Flyweight (object factory) pattern are useful to limit numbers of statements for controversial issues, objects of without, various types and to statements for controversial assist with object reuse and reduce garbage collection. The real-time specification for essays of christmas, Java allows 'new' to allocate objects in a 'current memory region', which may be other than the thesis statements for controversial, heap.
Each such region is of christmas, a type of MemoryArea, which can manage allocation. Using variables to provide access to thesis statements for controversial limited numbers of objects is efficient, but a maintenance problem if you need to change the object access pattern, for example from how to write a global singleton to issues a ThreadLocal Singleton. A non-static factory method is copy essay, polymorphic and so provides many advantages over static factory methods. Statements Issues? The Abstract Factory design pattern uses a single class to create more than one kind of object. An alternative to how to unit the Flyweight pattern is the Prototype pattern, which allows polymorphic copies of existing objects. The Object.clone() method signature provides support for the Prototype pattern.
Prototypes are useful when object initialization is expensive, and you anticipate few variations on the initialization parameters. Then you could keep already-initialized objects in a table, and clone an existing object instead of thesis issues, expensively creating a new one from scholarship application without scratch. Immutable objects can be returned directly when using Prototyping, avoiding the copying overhead. Timing out thesis statements for controversial, sockets (Page last updated 2000, Added 2001-06-18, Author David Reilly, Publisher JavaCoffeeBreak). Tips: Use a timer thread to scholarship without essays monitor socket activity and timeout if blocked.
Use the socket option SO_TIMEOUT, set by using the setSoTimeout() method, to automatically timeout blocked sockets. Deadlocks (Page last updated November 2000, Added 2002-04-26, Author Heinz M. Kabutz, Publisher Kabutz). Tips: Use CTRL+BREAK to for controversial get a thread dump when a deadlock occurs, to find where the deadlock is. Use SwingUtlities.invokeLater() to run any Swing GUI changes and avoid deadlocks, but note that this will hold up GUI processing while running, so make the run() call quick. Essay On Summer For Class 7? Use SwingUtilities.isEventDispatchThread() to test if can run code immediately without calling SwingUtlities.invokeLater(). Load testing of thesis issues, web applications (Page last updated June 2001, Added 2001-06-18, Author Frank Cohen, Publisher IBM).
Tips: Current Web-application architectures consists many small servers that are accessed through a load balancer, providing a front-end to essay for class 7 a powerful database server. This architecture provides a foundation for achieving good performance. Load testing of web applications should include: State machine testing (entries in for controversial a shopping basket, should still be there when checked out); Really long session testing (session started then continued several hours later); Hordes of savage users testing (users do lots nonsensical activity); Privileged testing (only some users should be able to access some functionality); Speed testing (do tasks complete within the essays critiquing article, required times?). Statements? Each type of test should be run with several different user loads. Test suites should be automated and scholarship application essays easily changed. [Article discusses Load , an open-source set of tools with XML scripting language] J2EE design patterns to issues improve performance (Page last updated June 2001, Added 2001-06-18, Author Daniel H. Essays Of Christmas? Steinberg, Publisher JavaWorld). Tips: Combine multiple remote calls for state information into thesis statements one call using a value object to on child in india wrap the data (the Value Object pattern, superceded by local interfaces in EJB 2.0).
Where long lists of data are returned by for controversial issues queries, use the Page-by-Page Iterator pattern: a server-side object that holds data on scholarship without essays the server and supplies batches of thesis statements for controversial issues, results to the client. Oracle JDBC tips (Page last updated December 2001, Added 2001-12-26, Author Donald Bales, Publisher OnJava). Tips: Although Oracle recommend using the OCI driver for optimal client side access, the writer finds the essays, Thin driver to have have better performance. Turn off autocommit, Connection.setAutoCommit(false). From the client side, Statement is faster than PreparedStatement (except if you are batching statements) when using dynamic SQL. Statements Issues? Use PreparedStatements for all, except dynamic, SQL statements. Use PreparedStatements for batching repetitive inserts or updates. OraclePreparedStatement.setExecuteBatch() (proprietary method) is the fastest way to execute batch statements. Use SQL's set based processing capabilities to operate on multiple rows simultaneuosly, rather than blindly operating on one row at a time as the simplest Java-RDB architectural mapping will produce. Chapter 19, Performance of Java Programming with Oracle JDBC (Page last updated December 2001, Added 2001-12-26, Author Donald Bales, Publisher O'Reilly). Tips: Performance should be considered at the start of scholarship application without essays, a project.
Use the EXPLAIN PLAN facility to thesis statements issues explain how the database's optimizer plans to execute your SQL statements, to identify performance improvements such as additional indexes. If more than one SQL statement is essays, executed by your program, you can gain a small performance increase by turning off auto-commit. It takes about 65 iterations of a prepared statement before its total time for thesis statements for controversial issues, execution catches up with a statement, because of prepared statement initialization overheads. Use PreparedStatements to batch statements for optimal performance. Copy Essay? The Thin driver is faster than the statements, OCI driver. Thesis On Child? This is contrary to thesis statements for controversial Oracle's recommendation. A SELECT statement makes two round trips to the database, the first for metadata, the second for data. Use OracleStatement.defineColumnType() to predefine the unit, SELECT statement, thus providing the JDBC driver with the issues, column metadata which then doesn't require the thesis in india, first database trip.
Given a simple SQL statement and a stored procedure call that accomplishes the same task, the simple SQL statement will always execute faster because the stored procedure executes the same SQL statement but also has the statements, overhead of the procedure call itself. Copy Essay? On the other hand complex tasks requiring several SQL statements can be faster using stored procedures as fewer network trips and data transfers will be needed. Database performance (Page last updated December 2001, Added 2001-12-26, Author Peter Varhol, Publisher JavaPro). Tips: Thoughtful page design makes for a better user experience by enabling the application to seem faster than it really is. Use the flush method associated with the out object to statements for controversial issues display static text and graphics on the browser page before the database query returns, to prevent the how to write unit, user from thesis issues having to look at a blank page for essays, a long time. ResultSet types affect updates.
TYPE_FORWARD_ONLY: no updating allowed; TYPE_SCROLL-SENSITIVE: update immediately; TYPE_SCROLL_INSENSITIVE: update when the connection is closed. (Concurrency type must be set to CONCUR-UPDATABLE to allow the table to be updated.) Performance can be better if changes to the database are batched: turn off autocommit; add multiple SQL statements using the statements issues, Statement.addBatch() method; execute Statement.executeBatch(). Scaled systems need optimized SQL calls, querying the right amount of essay without, data, and displaying pages before the query is complete. Prepared statements also speed up database access, and should be used if a statement is to be executed more than once. JDBC tutorial (requires free registration) (Page last updated November 2001, Added 2001-12-26, Author Robert J. Brunner, Publisher IBM). Tips: Type 1 (JDBC-ODBC-DB) drivers incur a performance penalty because of the bridging needed to reach the database. Thesis Statements For Controversial Issues? [Type 2 (JDBC-clientDBAgent-DB) drivers seem to have middling performance]. Type 3 (JDBC-Middleware-DB) drivers incur a performance penalty because of the bridging needed to reach the database, but does introduce optimization potential from the vacation for class 7, location of the middleware. Type 4 (JDBC-DB) drivers typically provide optimum driver performance.
The higher the level of transaction protection, the higher the performance penalty. Transaction levels in order of increasing level are: TRANSACTION_NONE, TRANSACTION_READ_UNCOMMITTED, TRANSACTION_READ_COMMITTED, TRANSACTION_REPEATABLE_READ, TRANSACTION_SERIALIZABLE. Issues? Use Connection.setTransactionIsolation() to set the desired tansaction level. The default autocommit mode imposes a performance penalty by making every database command a separate transaction. Turn off autocommit (Connection.setAutoCommit(false)), and explicitly specify transactions. Batch operations by thesis on child combining them in one transaction, and in one statement using Statement.addBatch() and Statement.executeBatch(). Savepoints (from JDBC3.0) require expensive resources. Release savepoints as soon as they are no longer needed using Connection.releaseSavepoint(). Each request for a new database connection involves significant overhead. This can impact performance if obtaining new connections occurs frequently. Reuse connections from connection pools to limit the cost of creating connections. [The tutorial lists all the overheads involved in issues creating a database connection].
The ConnectionPoolDataSource (from JDBC3.0) and PooledConnection interfaces provide built-in support for connection pools. Use setLogWriter() (from Driver, DataSource, or ConnectionPooledDataSource; from JDBC3.0) to in india help trace JDBC flow. Use Connection.setReadOnly(true) to optimize read-only database interactions. Use Connection.nativeSQL() to see how the SQL query will execute in the database to help ensure that the SQL is optimized. Advanced JDBC tutorial (requires free registration). Thesis For Controversial? (Page last updated November 2001, Added 2001-12-26, Author Robert J. Brunner, Publisher IBM).
Tips: PreparedStatement objects are compiled (prepared) by scholarship without essays the JDBC driver or database for faster performance, and accept input parameters so they can be reused with different data. Stored procedures are functions that execute inside a database which provides faster performance than plain SQL. Java supports stored procedures from CallableStatement objects. Performance optimizing design patterns for J2EE (Page last updated December 2001, Added 2001-12-26, Author Vijay Ramachandran, Publisher Sun). Tips: For read-only access to a set of thesis statements for controversial, data that does not change rapidly, use the Fast Lane Reader pattern which bypasses the EJBs and application essays uses a (possibly non-transactional) data access object which encapsulates access to the data. Use the Fast Lane Reader to read data from the server and display all of them in one shot. When you need to access a large remote list of objects, use the thesis, Page-by-Page Iterator pattern which sends smaller subsets of the data as requested until the client no longer want any more data. Essays Critiquing Article? Use the thesis for controversial issues, Page-by-Page Iterator to send lists of simple objects from EJBs to clients.
When the client would request many small data items which would require many remote calls to satisfy, combine the multiple calls into one call which results in a single Value Object which holds all the data required to thesis be transferred. Use the statements, Value Object to scholarship application without essays send a single coarse-grained object from the server to the client(s). Flicker-free graphics with the Mobile Information Device Profile (Page last updated July 2001, Added 2001-08-20, Author Eric Giguere, Publisher Sun). Tips: Use double buffering: draw into an offscreen buffer, then copy into thesis for controversial the display buffer. Copying buffers is very fast on most devices, while directly drawing to essays a display sometimes causes users to see a flicker, as individual parts of the display are updated. Double buffering avoids flickering by combining multiple individual drawing operations into a single copy operation. Thesis For Controversial? Use the essays, Canvas.isDoubleBuffered() method, to determine if double buffering is already automatically used: on some implementations the thesis for controversial issues, Canvas object's paint method is essays, already a Graphics object of an thesis for controversial issues offscreen buffer managed by essay on summer 7 the system. (The system then takes care of copying the offscreen buffer to the display.) Use javax.microedition.lcdui.Image class to create an offscreen memory buffer, and use Graphics to statements draw to the offscreen buffer and to on child rights copy the contents of the offscreen buffer onto the display. The offscreen buffer is created by statements calling one of the Image.createImage methods.
Double buffering does have some overhead: if only making small changes to the display, it might be slower to use double buffering. On some systems image copying isn't very fast and flicker can can happen even with double buffering. Keep the number of essays of christmas, offscreen buffers to a minimum. There is thesis issues, a memory penalty to pay for essays, double buffering: the offscreen memory buffer can consume a large amount of memory. For Controversial Issues? Free the offscreen buffer whenever the canvas is hidden (use the canvas' hideNotify() and showNotify() methods.) Some killer quotes, leading to the odd tip. (Page last updated 2000, Editor Elliotte Rusty Harold, Publisher IBiblio).
Tips: A Vector may be convenient and generalized, but it's almost always overkill, and you pay the price for for class 7, it in speed and other ways. --Greg Guerin on the MRJ-dev mailing list A lot of statements for controversial, speed (or memory) can go down the drain if the underlying structure is a poor fit to how to write unit the problem, or is inefficient for a particular program's common actions. --Greg Guerin on thesis for controversial issues the MRJ-dev mailing list It is perfectly legal for available() to always return 0, even when there are a zillion bytes available, and in essays of christmas fact the statements for controversial, default implementation in Inputstream.available() does just that. --Thomas Maslen on of christmas the mrj-dev mailing list Seeing the wrong solution to a problem (and understanding why it is wrong) is often as informative as seeing the correct solution. Thesis Statements For Controversial Issues? --W. Richard Stevens You need to run your full QA cycle on _all_ platforms you plan on supporting your app on . real software releases need to be tested on a large variety of different systems and OS versions because there _are_ differences. Just like there are differences between different Java implementations. Essays? --Jens Alfke on the mrj-dev mailing list I often find with Java that if you run the issues, same program twice, the second run is significantly faster, presumably because the JVM is remembering something. --Michael Kay on unit the xsl-list mailing list Java isn't inherently slow, it just encourages a create and forget [objects] type of programming which is. Thesis? --Oren Ben-Kiki on the XSL mailing list Java does not expose many of the I/O capabilities that are synonymous with high performance. Examples include memory mapped files and asynchronous I/O. Heck, it doesn't even expose non-blocking I/O. --Gabe Beged-Dov on essay without the xml-dev mailing list I/O performance issues, usually overshadow all other performance issues making them the first area to concentrate on when tuning performance. Unfortunately, optimal reading and thesis statements for controversial issues writing can be challenging in Java. --Daniel Lord and Achut Reddy, http://www.sun.com/workshop/java/wp-javaio/ Streamlining the use of I/O often results in greater performance gains than all other possible optimizations combined. --Daniel Lord and Achut Reddy http://www.sun.com/workshop/java/wp-javaio/ Modern super-scalar processors with deep memory hierarchies and complex compiler optimization stages make it *extremely* difficult to thesis rights in india predict which code or data structure variant is more efficient.
Old rules of thumb and statements for controversial common sense are not of much use any more for distinguishing more and less performant algorithms of comparable complexity on essays critiquing a late 1990s processor. Surprises are frequent. Design decisions on performance grounds should today only statements for controversial, be made after real measurements and much of essays of christmas, what you learned 10 years ago about manual optimization is obsolete these days. --Markus Kuhn on the Unicode mailing list Most Java VM implementations search the interface list back to front so that most often used interface should be the last interface in the 'implements' list. Thesis Statements Issues? --Don Park on the xml-dev mailing list. Article about optimizing I/O performance. (Page last updated November 2000, Added 2000-12-20, Author Brian Goetz, Publisher JavaWorld). Tips: Measure early, measure often. You can't effectively manage performance if you don't know the source of your problem. Spending days tuning a subsystem that accounts for 1 percent of an application's total runtime simply cannot yield more than a 1 percent improvement in write unit application performance. For Controversial? Use performance measurement tools to identify where your application spends its time and focus your energy on those hot spots. Object creation is an expensive operation: avoid excessive object instantiations. Application? Use buffered I/O (with buffering classes or by explicitly buffering to an array). Thesis Statements For Controversial Issues? InputStream runs faster than Reader.
Combine tasks from multiple classes to avoid extra overhead and redundant object creation. Particle's pretty good coverage of the main Java data structures. Only a few tuning tips: reuse, pools, optimized sorting. But knowing which structure to use for a particular problem is an important performance tuning technique. (Page last updated April 2000, Added 2000-12-20, Author J. Particle, Publisher Particle). Tips: Make linked lists faster by having dummy first and last nodes. How To Write? Reusing code is thesis for controversial issues, easier than reimplementing, but can lead to slower performance. Thesis Rights In India? Use node pools to reduce memory impact. Sorting elements on insertion means they don't need to statements for controversial issues be sorted later. Of Christmas? [Article includes several(non-optimized) standard sort algorithms implemented in thesis for controversial Java, and compares their performance.] [Article discusses optimizing a quicksort.] If you are using many small collections, carefully consider the collection structure used. Some structures may have large memory overheads that should be avoided in essays critiquing article this case. Some discussion of hidden surface removal for graphics.
Article on recycling resource pools (Page last updated 1998, Added 2000-12-20, Authors Philip Bishop and thesis for controversial Nigel Warren, Publisher JavaWorld). Tips: Check for broken resources when putting them back in the pool. Use the builder pattern: break the construction of how to write unit, complex objects into a series simpler Builder objects, and a Director object which combines the Builders to statements issues form the complex object. Then you can use Recycler (a type of Director) to replace only the broken parts of the complex object, so reducing the amount of objects that need to be recreated. Article on building an object pool for improved performance. Essays Of Christmas? (Page last updated June 1998, Added 2000-12-20, Author Thomas E. Davis, Publisher JavaWorld). Statements For Controversial? Tips: [Article discusses generic pool issues including storage, tracking, and expiration times of pool elements.] Use connection pools to recycle connections and reduce overheads [Article includes a JDBC connection pool implementation.] Article on scholarship improving object pools performance. (Page last updated September 1998, Added 2000-12-20, Author Thomas E. Davis, Publisher JavaWorld). Tips: Use an expiration thread to clean up excessive amounts of objects in the pool. Use java.lang.ref.Reference objects to determine when objects checked out thesis statements for controversial issues, but never checkd in have been released by the application.
Limiting the size of the pool can adversely impact performance. Optimizing JDBC (Page last updated August 2001, Added 2001-08-20, Author John Goodson, Publisher Java Developers Journal). Without? Tips: Minimize the use of Metadata: Cache all metadata as they will not change; Avoid using null arguments in metadata methods; Use a dummy query with getMetadata() rather than getColumns(). Retrieve data as efficiently as possible: Minimize the amount of data returned by the query; Don't make average users pay the same query cost of the users with extensive query requirements; Remember that users seldom want to see too much data in one go; Use setMaxRows(), setMaxFieldSize(), and SetFetchSize(); Decrease the column size; Use the smallest packet size that will meet your needs (if the driver supports packet sizing). Use a parametrized remote procedure call (RPC) rather than passing parameters as part of the for controversial, RPC call, e.g. use Connection.prepareCall(Call getCustName (?)).setLong (1,12345) rather than Connection.prepareCall(Call getCustName (12345)) Minimize connections; try to reuse connections. Turn autocommit off. Avoid using distributed transactions. Use getBestRowIndentifier() to determine the optimal set of columns to use in the Where clause for essays, updating data. (The columns returned could be pseudo-columns that can provide pointers to the exact location of the thesis statements for controversial, data, and are not obtained by getColumns().) EJB performance tips (Page last updated November 2001, Added 2001-12-26, Authors Ravi Kalidindi and Rohini Datla, Publisher PreciseJava). Tips: EJB calls are expensive.
A method call from the client could cover all the following: get Home reference from the NamingService (one network round trip); get EJB reference (one or two network roundtrips plus remote creation and initialization of without essays, Home and EJB objects); call method and return value on statements for controversial issues EJB object (two or more network rountrips: client-server and [mutliple] server-db; several costly services used such as transactions, persistence, security, etc; multiple serializations and deserializations). Rights In India? If you don't need EJB services for thesis statements issues, an object, use a plain Java object and not an EJB object. How To Unit? Use Local interfaces (from EJB2.0) if you deploy both EJB Client and EJB in thesis the same JVM. (For EJB1.1 based applications, some vendors provide pass-by-reference EJB implementations that work like Local interfaces). Wrap multiple entity beans in a session bean to change multiple EJB remote calls into one session bean remote call and essay vacation several local calls (pattern called SessionFacade). Change multiple remote method calls into one remote method call with all the data combined into a parameter object. Control serialization by modifying unnecessary data variables with 'transient' key word to avoid unnecessary data transfer over network. Cache EJBHome references to avoid JNDI lookup overhead (pattern called ServiceLocator).
Declare non-transactional methods of session beans with 'NotSupported' or 'Never' transaction attributes (in the ejb-jar.xml deployment descriptor file). Transactions should span the minimum time possible as transactions lock database rows. Set the for controversial, transaction time-out (in the ejb-jar.xml deployment descriptor file). Use clustering for scalability. Essay Vacation For Class? Tune the EJB Server thread count. Use the HttpSession object rather than a Stateful session bean to maintain client state. Thesis Statements Issues? Use the ECperf benchmark to essays help differentiate EJB server performances. Tune the for controversial issues, Stateless session beans pool size to of christmas minimize the creation and destruction of beans. Use the statements for controversial issues, setSessionContext() or ejbCreate() method to essays cache bean specific resources. Release acquired resources in the ejbRemove() method.
Tune the statements for controversial, Stateful session beans cache size to and time-out minimize activations and passivations. Allow stateful session beans to be removed from the container cache by explicitly using the remove() method in the client. Tune the in india, entity beans pool size to minimize the creation and destruction of beans. Tune the entity beans cache size to minimize the thesis statements, activation and passivation of beans (and associated database calls). Essays Article? Use the setEntityContext() method to cache bean specific resources and release them from the unSetEntityContext() method. Use Lazy loading to avoid unnecessary pre-loading of child data. Choose the lowest cost transaction isolation level that avoids corrupting the data.
Transaction levels in increasing cost are: TRANSACTION_READ_UNCOMMITED, TRANSACTION_READ_COMMITED, TRANSACTION_REPEATABLE_READ, TRANSACTION_SERIALIZABLE. Issues? Use the lowest cost locking available from the database that is consistent with any transaction. Of Christmas? Create read-only entity beans for issues, read only operations. Essay On Summer Vacation For Class? Use a dirty flag where supported by the EJB server to thesis for controversial avoid writing unchanged EJBs to the database. Commit the data after the on summer vacation, transaction completes rather than after each method call (where supported by EJB server). Statements? Do bulk updates to reduce database calls. Use CMP rather than BMP to utilize built-in performance optimization facilities of CMP. Use ejbHome() methods for global operations (from EJB2.0). Tune the essays, connection pool size to thesis for controversial minimize the creation and destruction of database connections.
Use JDBC directly rather than using entity beans when dealing with large amounts of data such as searching a large database. Combine business logic with the entity bean that holds the data needed for that logic to process. Tune the essays, Message driven beans pool size to optimize the concurrent processing of messages. Statements? Use the setMesssageDrivenContext() or ejbCreate() method to cache bean specific resources, and release those resources from the ejbRemove() method. JDBC performance tips (Page last updated November 2001, Added 2001-12-26, Authors Ravi Kalidindi and Rohini Datla, Publisher PreciseJava). Tips: Use the fastest driver available to the database: normally type 4 (preferably) or type 3. Tune the critiquing article, defaultPrefetch and defaultBatchValue settings. Get database connections from a connection pool: use javax.sql.DataSource for optimal configurability.
Use the vendor's connection pool; or ConnectionPoolDataSource and PooledConnection from JDBC2.0; or a proprietary connection pool. Statements Issues? Batch your transactions. Turn off autocommit and thesis in india explicitly commit a set of thesis, statements. Choose the fastest transaction isolation level consistent with your application requirements. Levels from fastest to slowest are: TRANSACTION_NONE, TRANSACTION_READ_UNCOMMITED, TRANSACTION_READ_COMMITED, TRANSACTION_REPEATABLE_READ, TRANSACTION_SERIALIZABLE. Close resources (e.g. connections) when finished with them.
Use a PreparedStatement when you execute the essays, same statement more than once. Use CallableStatement to execute stored procedures. Thesis For Controversial? This is faster than a prepared statement, but loses database independence (stored procedures are not standardized unlike SQL). Copy? Batch updates and accesses with Statements and ResultSets (with executeBatch() and setFetchSize()). Set up the proper direction for processing rows. Use the proper getXXX() methods. Write SQL queries that minimize the data returned. Cache read-only and read-mostly tables data. Use the Page-by-Page Iterator pattern to repeatedly pass small amounts of data rather than huge chunks. Servlet performance tips (Page last updated November 2001, Added 2001-12-26, Authors Ravi Kalidindi and Rohini Datla, Publisher PreciseJava).
Tips: Use the servlet init() method to cache static data, and release them in the destroy() method. Thesis? Use StringBuffer rather than using + operator when you concatenate multiple strings. Use the print() method rather than the println() method. Use a ServletOutputStream rather than a PrintWriter to send binary data. Thesis On Child Rights? Initialize the PrintWriter with the optimal size for pages you write. Flush the data in statements sections so that the user can see partial pages more quickly.
Minimize the synchronized block in the service method. Thesis On Child Rights In India? Implement the getLastModified() method to use the browser cache and the server cache. Use the application server's caching facility. Session mechanisms from fastest to slowest are: HttpSession, Hidden fields, Cookies, URL rewriting, the persistency mechanism. For Controversial? Remove HttpSession objects explicitly in your program whenever you finish the session. Set the unit, session time-out value as low as possible. Use transient variables to thesis reduce serialization overheads.
Disable the servlet auto reloading feature. How To Write Unit? Tune the thread pool size. High load web servlets (Page last updated July 2002, Added 2002-07-24, Author Pier Fumagalli, Publisher OnJava). Tips: Hand off requests for static resources directly to statements for controversial issues the web server by specifying the URL, not by redirecting from the servlet. Use separate webservers to on child deliver static and statements issues dynamic content. Cache as much as possible. Make sure you know exactly how much RAM you can spare for caches, and have the right tools for measuring memory. Load balance the how to, Java application using multiple JVMs.
Use ulimit to monitor the number of file descriptors available to the processes. Make sure this is thesis for controversial, high enough. Logging is more important than the performance saved by rights not logging. Monitor resources and prepare for spikes. JSP performance tips (Page last updated November 2001, Added 2001-12-26, Authors Ravi Kalidindi and Rohini Datla, Publisher PreciseJava). Tips: Use the jspInit() method to cache static data, and statements release them in the jspDestroy() method. Use the jspInit() method to cache static data. Use StringBuffer rather than using + operator when you concatenate multiple strings. Use the print() method rather than the println() method.
Use a ServletOutputStream rather than a PrintWriter to send binary data. Without? Initialize the PrintWriter with the thesis issues, optimal size for pages you write. Flush the data in sections so that the application without, user can see partial pages more quickly. Minimize the thesis statements for controversial issues, synchronized block in the service method. Avoid creating a session object with the directive %@ page session=false % Increase the buffer size of System.out with the directive %@ page buffer=12kb % Use the include directive instead of the include action when you want to include another page. Minimize the scope of the 'useBean' action. Custom tags incur a performance overhead. Use as few as possible.
Use the essays, application server's caching facility, and the session and for controversial application objects (using getAttribute()/setAttribute()). Scholarship Application Without Essays? There are also third-party caching tags available. Session mechanisms from fastest to slowest are: session, Hidden fields, Cookies, URL rewriting, the persistency mechanism. Remove 'session' objects explicitly in your program whenever you finish the session. Thesis Statements For Controversial? Reduce the essay, session time-out as low as possible.
Use 'transient' variables to thesis reduce serialization overheads. Application Without? Disable the JSP auto reloading feature. Tune the thread pool size. JMS performance tips (Page last updated November 2001, Added 2001-12-26, Authors Ravi Kalidindi and Rohini Datla, Publisher PreciseJava). Tips: Start the statements issues, consumer before you start the producer so that the initial messages do not need to queue. Use a ConnectionConsumer to process messages concurrently with a ServerSessionPool. Copy Essay? Close resources (e.g. connections, session objects, producers, consumers) when finished with them. DUPS_OK_ACKNOWLEDGE and statements AUTO_ACKNOWLEDGE perform better than CLIENT_ACKNOWLEDGE.
Use separate transactional sessions and non-transactional sessions for essays of christmas, transactional and non-transactional messages. Statements Issues? Tune the in india, Destination parameters: a smaller capacity increases message throughput; a higher redelivery delay and lower redelivery limit reduces the thesis statements for controversial issues, overhead. Choose non-durable (NON_PERSISTENT) messages wherever appropriate to avoid the persistency overhead. Set the TimeToLive value as low as feasible (default is for messages to never expire). Receive messages asynchronously with a MessageListener implementation. Choose the message type that minimizes memory overheads. Use 'transient' variables to reduce serialization overheads. Pattern performance tips (Page last updated November 2001, Added 2001-12-26, Authors Ravi Kalidindi and Rohini Datla, Publisher PreciseJava). Tips: The ServiceLocator/EJBHomeFactory Pattern reduces the expensive JNDI lookup process by caching EJBHome objects. The SessionFacade Pattern reduces network calls by scholarship combining accesses to multiple Entity beans into one access to the facade object.
The MessageFacade/ServiceActivator Pattern moves method calls into thesis issues a separate object which can execute asynchronously. The ValueObject Pattern combines remote data into one serializable object, thus reducing the number of network transfers required to access multiple items of remote data. The ValueObjectFactory/ValueObjectAssembler Pattern combines remote data from multiple remote objects into one serializable object, thus reducing the number of network transfers required to access multiple items of remote data. Write? The ValueListHandler Pattern: avoids using multiple Entity beans to access the database, using Data Access Objects which explicitly query the database; and returns the data to the client in batches (which can be terminated) rather than in thesis for controversial issues one big chunk, according to the Page-by-Page Iterator pattern. The CompositeEntity Pattern reduces the number of actual entity beans by wrapping multiple java objects (which could otherwise be Entity beans) into one Entity bean.
Writing a seamless audio looper (Page last updated August 2001, Added 2001-08-20, Author Greg Travis, Publisher EarthWeb). Tips: Switching audio streams from one piece of sound to another requires some fiddly managing of the transition delay in essays critiquing article order to thesis for controversial issues avoid a gap in the audio output. On Child? To avoid the thesis statements, transition delay, you need to: flush the output buffer; find out essays of christmas, how much data was dumped; add a fudge factor; and thesis combine these values to determine from where to essay without start playing the new audio stream. Generating code dynamically (Page last updated February 2002, Added 2002-02-22, Author Norman Richards, Publisher Java Developers Journal). Tips: Compiling code into classes at runtime, such as for for controversial, JSP pages, provides excellent flexibility with almost no performance overhead. XSLTC can compile XSL stylesheets to speed up transforming XML input files.
If a complex interpreted procedure is on summer 7, expected to be used more than once, it can be more efficient to convert the procedure into thesis issues an expression tree which will apply the procedure optimally. Converting a complex interpreted procedure into code that can be compiled, then using a compiled version normally results in the fastest execution times for critiquing, the procedure. Sun's javac is not a very efficient compiler. Faster compilers are available, such as jikes. Compiling code at statements for controversial runtime can take a significant amount of critiquing article, time. If the compile time needs to be minimized, it is important to use the fastest compiler available. An in-memory compiler is for controversial, significantly faster than compiling code using an external out-of-process Java compiler.
Generating bytecode directly in-process is essays critiquing article, significantly faster than compiling code using an external out-of-process Java compiler, and is also faster than using an thesis statements issues in-memory compiler. BCEL, the Bytecode Engineering Library, is essays of christmas, one possible bytecode generator. Java 3D performance tips (Page last updated June 2001, Added 2001-08-20, Author Doug Twilleager, Publisher J3D). Tips: Once an application calls BranchGroup.compile() or SharedGroup.compile(), only objects with their capability bits set can be modified. Use capability bits to describe which objects change at runtime, so that J3D can optimize the thesis statements for controversial issues, app.
Only set capability bits when needed, to let J3D maximally optimize performance. Set the essays article, bounds of objects so that J3D can ignore objects outside target object spatial scopes. Reorder leaf nodes for the most efficient rendering. When rendering check only the changes in rendering characteristics rather than all characteristics. Minimize the number of thesis issues, Shape3D nodes, but don't combine while ignoring spatial locality. Use the stripifier, or manually stripify the essay on summer for class 7, application: try to convert the geometry into for controversial long strips of triangles rather than fans of triangles. Share Appearance/Texture/Material NodeComponent objects when possible. Essays? Set the thread priorities appropriately, or use the default priority. Minimize thread activity.
Note the performance effects of the J3D threads, specifically Behaviors, Collision and Sounds. J3D fully supports multi-processor machines. Statements? Use native threads where possible. Use application knowledge to turn off currently non-visible Switch nodes. Use a Switch node to animate a sprite by putting all the animation frames under one Switch node and using a SwitchValueInterpolator. This increases memory consumption in favor of copy essay without, smooth animations. Unordered groups are faster than ordered groups. Thesis Statements? LOD Behaviors can be to reduce geometry rendering requirements with lower levels of detail. Use bounds based picking rather than geometry based picking. Transform the of christmas, ViewPlatform rather than every object for a scene transformation. The Verified Service Locator pattern (Page last updated July 2002, Added 2002-07-24, Author Paulo Caroli, Publication JavaWorld, Publisher JavaWorld).
Tips: The Service Locator pattern improves performance by caching service objects that have a high-lookup cost. The Service Locator pattern has a problem in that cached objects may become invalid without the thesis for controversial, service locator knowing. The Verified Service Locator pattern periodically tests the validity of the caches objects to essays of christmas avoid providing invalid service objects to requestors. Sun Community chat on Java BluePrints (Page last updated May 2002, Added 2002-07-24, Author Edward Ort, Publication Sun Developer, Publisher Sun). Tips: For very large transactions, use transaction attribute TX_REQUIRED for EJB methods to have all the method calls in a call chain use the same transaction.
Make tightly coupled components local to statements issues each other. Put remote beans primarily as facades across subsystems. Critiquing? The page-by-page pattern is designed to handle cases where the result set is large, and for controversial the end-user is rights, not interested in seeing all of the results. There is really no upper threshold for statements for controversial, the size of result set in the pattern. Clustering with JBoss (Page last updated July 2002, Added 2002-07-24, Authors Bill Burke, Sacha Labourey, Publisher OnJava). Tips: A hardware- or software-based HTTP load-balancer usually sits in front of the application servers within a cluster. The load balancer can decrypt HTTPS requests and distribute load.
HTTP session replication is expensive for essay, a J2EE application server. If you can live with forcing a user to log in thesis for controversial issues again after a server failure, then an HTTP load-balancer probably provides all of the fail-over and on summer load-balancing functionality you need. If you are storing things other than EJB Home references in your JNDI tree, then you may need clustered JNDI. 24/7 availability needs the ability to hot-deploy and undeploy new applications and new versions, and to apply patches, without bringing down the application server for maintenance. Smart proxies can be used to implement load-balancing and fail-over for EJB remote clients. These proxies manage a list of available RMI connections one of which it will use to thesis for controversial issues service an invocation. Speeding web page downloads using compression (Page last updated July 2002, Added 2002-07-24, Author Steven Chau, Publication HttpRevealer.com, Publisher HttpRevealer.com). Tips: Browsers sending Accept-Encoding: gzip will accept gziped compressed pages. Return the thesis on child, page compressed with Content-Encoding: gzip using GZIPOutputStream. For Controversial Issues? Use a servlet filter to essay on summer vacation for class transparently compress pages to browsers that accept compressed pages. Optimizing JDBC Prepared Statments.
Also a followup discussion at http://www.theserverside.com/discussion/thread.jsp?thread_id=8013 (Page last updated July 2001, Added 2001-08-20, Author ?, Publisher The Server Side). Tips: Databases analyze query statements to decide how to process them most optimally, then cache the resulting query plan, keyed on the full statement. Reusing identical statements reuses the query plan. Altering the statement causes a new query plan to be generated for each new statement. However statements with parameters can have the query plan reused, so use parameters rather than regenerating the thesis statements for controversial issues, statement with different values. Critiquing Article? Using a new connection requires a prepared statement to issues be recreated. Reusing connections allows a prepared statement to be reused.
Connection pools should have associated PreparedStatement caches so that the PreparedStatements are automatically reused. Swing performance tips (Page last updated 1999, Added 2001-05-21, Author Bill Harlan, Publisher Harlan). Tips: Redraw events can easily be generated faster than the redraw can execute. Ignore redraw events (or block their generation) until the current redrw is on summer, finished. Don't up redraw events.
Consider holding redraw events for a few milliseconds to see if it can be discarded due to getting another redraw event. Thesis Issues? If possible, consider drawing to off-screen buffers, and execute copies from that buffer in response to redraws, rather than actualy redrawing. Essays? Extend from for controversial JPanel, not Canvas; override paintComponent(), not paint(). Action listeners are all executed in the one event-dispatching thread. Time-consuming listeners should execute their work in essays of christmas a separate thread and thesis statements should avoid blocking the essays critiquing article, event-dispatching thread. (To reenter the event-dispatching thread calling SwingUtilities.invokeLater() or invokeAndWait()). Add event listeners after initialization of components have finished. Swing performance tips (Page last updated March 2001, Added 2001-05-21, Author Steve Wilson, Publisher Sun). Thesis Statements Issues? Tips: Use the latest version of Swing available, as the Swing development team have an ongoing project tp improve performance. When JScrollPane is scrolled, the entire visible contents of the scroll pane are redrawn. A backing store (off screen buffer) can be enabled using setBackingStoreEnabled(true) to speed up redraws, but this has some limitations: an extra buffer to copy can be significant for simple drawing operations; the backing store doesn't work when scrollRectToVisible() is called directly by the programmer (depends on Swing version); extra RAM is needed to maintain the extra backing buffer. Use window blitting (may be default depending on Swing version) enabled with scrollpane.getViewport().putClientProperty(EnableWindowBlit, Boolean.TRUE).
Enable outline dragging (no redrawing while dragging) with JDesktopPane.putClientProperty(JDesktopPane.dragMode, outline). Enable faster dragging using blitting with JDesktopPane.putClientProperty(JDesktopPane.dragMode, faster). Chapter 10, Serialization from Java RMI (Page last updated November 2001, Added 2001-12-26, Author William Grosso, Publisher OnJava). Tips: Use transient to essays avoid sending data that doesn't need to be serialized. Serialization is a generic marshalling mechanism, and generic mechanisms tend to be slow. Statements Issues? Serialization uses reflection extensively, and this also makes it slow. Serialization tends to generate many bytes even for small amounts of data.
The Externalizable interface is provided to solve Serialization's performance problems. Externalizable objects do not have their superclass state serialized, even if the superclass is Serializable. This can be used to reduce the data written out vacation for class 7, during serialization. Issues? Use Serializable by default, then make classes Externalizable on a case-by-case basis to improve performance. Web application scalability. (Page last updated June 2000, Added 2001-05-21, Author Billie Shea, Publisher STQE Magazine). Tips: Web application scalability is the essay vacation for class 7, ability to sustain the required number of simultaneous users and/or transactions, while maintaining adequate response times to end users. Issues? The first solution built with new skills and new technologies will always have room for improvement. Avoid deploying an application server that will cause embarrassment, or that could weaken customer confidence and business reputation [because of bad response times or lack of calability]. Consider application performance throughout each phase of development and into production.
Performance testing must be an integral part of designing, building, and maintaining Web applications. There appears to be a strong correlation between the use of performance testing tools and the likelihood that a site would scale as required. Scholarship Essays? Automated performance tests must be planned for and iteratively implemented to identify and remove bottlenecks. Statements For Controversial Issues? Validate the architecture: decide on the maximum scaling requirements and then performance test to validate the necessary performance is achievable. This testing should be done on the prototype, before the application is thesis on child rights in india, built. Thesis? Have a clear understanding of how easily your configurations of Web, application, and/or database servers can be expanded.
Factor in load-balancing software and/or hardware in order to essays critiquing efficiently route requests to the least busy resource. Consider the effects security will have on performance: adding a security layer to transactions will impact response times. For Controversial Issues? Dedicate specific server(s) to handle secure transactions. Essay On Summer Vacation 7? Select performance benchmarks and use them to quantify the scalability and determine performance targets and future performance improvements or degradations. Thesis Statements For Controversial Issues? Include all user types such as information-gathering visitors or transaction visitors in your benchmarks. Perform Performance Regression Testing: continuously re-test and measure against the established benchmark tests to copy without ensure that application performance hasn?t been degraded because of the changes you?ve made.
Performance testing must continue even after the application is for controversial issues, deployed. For applications expected to perform 24/7 inconsequential issues like database logging can degrade performance. Continuous monitoring is key to spotting even the slightest abnormality: set performance capacity thresholds and monitor them. When application transaction volumes reach 40% of maximum expected volumes, it is time to start executing plans to essay vacation expand the system. Web Load Test Planning (Page last updated April 2001, Added 2001-05-21, Author Alberto Savoia, Publisher STQE Magazine). Thesis For Controversial? Tips: The only reliable way to thesis on child rights in india determine a system?s scalability is to perform a load test in statements for controversial which the volume and characteristics of the anticipated traffic are simulated as realistically as possible. It is hard to design and essays critiquing article develop load tests that come close to matching real loads. Characterize the anticipated load as objectively and systematically as possible: use existing log files where possible; characterize user sessions (pages viewed - number and types; duration of thesis statements issues, session; etc). Determine the range and distribution of variations in sessions. Don't use averages, use representative profiles. Estimate target load and peak levels: estimate overall and peak loads for the server and expected growth rates.
Estimate how quickly target peaks levels will be reached, and for how long they will be sustained. The duration of the peak is important and the server must be designed to vacation for class handle it. The key elements of a load test design are: test objective (e.g. can the server handle N sessions/hr peak load level?); pass/fail criteria (e.g. pass if response times stay within define values); script description (e.g. user1: page1, page2, . Thesis? ; user2: page1, page3, start transaction1, etc); scenario description (which scripts at which frequency, and how load increases). Performance chapter (chapter 20) from Professional JSP 2nd Edition (Page last updated August 2001, Added 2001-10-22, Author Simon Brown, Robert Burdick, Darko Cokor, Jayson Falkner, Ben Galbraith, RodJohnson, Larry Kim, Casey Kochmer, Thor Kristmundsson, Sing Li, Dan Malks, Mark Nelson, Grant Palmer, Bob Sullivan, Geoff Taylor, John Timney, Sameer Tyagi, Geert Van Damme, Steve Wilkinson, Publisher The Server Side). Tips: The user's view of the response time for a page view in his browser depends on download speed and on write unit the complexity of the statements, page. e.g. the number of graphics. A poorly-designed highly graphical dynamic website could be seen as 'slow' even if the web downloads are individually quite fast. No web application can handle an unlimited number of requests; the trick in optimization is to anticipate the likely user demand and ensure that the web site can gracefully scale up to the demand while maintaining acceptable levels of speed. Profile the server to identify the bottlenecks. Essays Critiquing Article? Note that profiling can be done by instrumenting the for controversial, code with measurement calls if a profiler is unavailable. One stress test methodology is: determine the maximum acceptable response time for essays of christmas, getting a page; estimate the maximum number of for controversial, simultaneous users; simulate user requests, gradually adding simulated users until the web application response delay becomes greater than the acceptable response time; optimize until you reach the desired number of copy essay, users. Pay special attention to thesis issues refused connections during your stress test: these indicate the servlet is overwhelmed.
There is little performance penalty to using an MVC architecture. Use resource pools for expensive resources (like database connections). Critiquing? Static pages are much faster than dynamic pages, where the web server handles static pages separately. Servlet filtering has a performance cost. Test to see if it is an acceptable cost.
Ensure that the webserver is configured to handle the expected number of thesis for controversial, user for example: enough ready sockets; enough disk space; enough CPU. Use the fastest JVM you have access to. Chapter 3 of High Performance Java Computing : Multi-Threaded and Networked Programming, Race Conditions and Mutual Exclusion (Page last updated January 2001, Added 2001-02-21, Authors George Thiruvathukal, Thomas Christopher, Publisher Sun). Essays Article? Tips: Execute I/O in blocks rather than one byte at a time. I/O reads are normally faster than writes. This means that I/O performance can be improved by decoupling reading and writing to dedicated threads, rather than interleaving reads and writes.
NOTE THE TIP volatile primitive datatypes have atomic ++ operations HAS BEEN SHOWN TO BE INVALID [The chapter describes implementations for lock objects (wait until unlocked), counting semaphore objects (wait until positive), barrier sempahore objects (wait until last thread is finished), future objects (wait until a variable is first set). These do not directly improve performance, but provide useful techniques for for controversial, synchronizing threads that assist a multi-threaded program in scholarship without being efficient]. Use resource enumeration (acquire resources in thesis a set order) to avoid deadlocks. Chapter 4 of High Performance Java Computing : Multi-Threaded and Networked Programming, Monitors (Page last updated January 2001, Added 2001-02-21, Authors George Thiruvathukal, Thomas Christopher, Publisher Sun). Tips: Java monitors are not necessarily the most efficient synchronization mechanism, especially if transferring the lock can lead to a race condition [chapter discusses a more complete Monitor class]. volatile fields can be slower than non- volatile fields, because the system is for class 7, forced to thesis for controversial store to memory rather than use registers. But they may useful to how to avoid concurrency problems. [The chapter discusses various policies for synchronizing threads trying to read from or write to shared resources, which provide different scheduling policies: one thread at a time; readers-preferred (readers have priority); writers-preferred (writers have priority); alternating readers-writers (alternates between a single writer and a batch of readers); take-a-number (first-come, first-served)]. Benchmarking JMS (Page last updated March 2001, Added 2001-03-21, Author Dave Chappell, Bill Wood, Publisher Java Developers Journal). Tips: Scaling middleware exposes a number of thesis statements for controversial, issues such as threading contention, network bottlenecks, message persistence issues, memory leaks, and overuse of object allocations. [Article dicusses questions to how to unit ask when setting up benchmarks for messaging middleware]. Message traffic under high-volume conditions are unpredictable and bursty. Messages can be produced far faster than they can be consumed, causing congestion.
This condition requires the message sends to be throttled with flow control (could be an exception, or an automatic resend). When testing performance, run overnight and over thesis weekends to generate longer term trends. Some concerns are: testing without a real network connection can give false measures; low user simulation can be markedly different from high user simulations; network throughput may be large than the deployed environment; nonpersistent message performance is dependent on processor and memory; disk speed is crucial for persistent messages. [Article provides a benchmark harness for testing JMS]. Designing Java Performance: reducing object creation (Page last updated March 2001, Added 2001-03-21, Author Brian Goetz, Publisher JavaWorld). Tips: Watch out for method interfaces which force unnecessary or inefficient object creation. Immutable objects are inefficient if you want to alter their structure, but efficient for sharing.
One way to avoid creating objects simply for on summer for class 7, information is to provide finer-grained methods which return information as primitives. This swaps object creation for statements for controversial issues, increased method calls. A second technique to avoid creating objects is to provide methods which accept dummy information objects that have their state overwritten to rights pass the information. A third technique to avoid creating objects is to statements issues provide immutable classes with mutable subclasses, by having state defined as protected in the superclass, but with no public updators. The subclass provides public updators, hence making it mutable. Don't try to speed up the essays of christmas, application if there is no performance problem. Some performance tips (Page last updated January 2001, Added 2001-01-19, Author Shyam Lingegowda, Publisher The Server Side). Tips: Use buffering for files stream i/o . Statements Issues? Use byte streams (not char-streams) for unit, ASCII characters. Recycle objects wherever possible.
Factor out constant computations from thesis issues loops. For Servlets, push one time computations into the init() method. Use StringBuffer when dealing with mutable strings. Essay Without? Initialize the StringBuffer with proper size. Let the compiler do compile time string concatenation.
Comparison of two string objects is faster if they differ in length. StringTokenizer is slow. Thesis For Controversial Issues? minimize the number of objects you create. Avoid initializing twice. Order boolean expressions so that they execute as fast as possible. ArrayList is application without essays, faster than Vector.
Minimize calls to Date and for controversial issues related classes. Expiring cached data (Page last updated January 2001, Added 2002-01-25, Author William Grosso, Publisher OnJava). Tips: Caching data on the client can improve performance, reduce communication overheads and increase the scalability of an application. Of Christmas? Be careful when caching information that the cache doesn't contain out-of-date or incorrect information. Thesis For Controversial? Servlet sessions expire after a settable timeout, but screens that automatically refresh can keep a session alive indefinitely, even when the screen is no longer in use.
Database connection pools can take one of essays, two strategies: a limited size pool, where attempts to thesis statements issues make connections beyond the pool size must wait for a connection to application become idle; or a flexible sized pool with a preferred size which removes idle connections as soon as the preferred size is exceeded (i.e. temporarily able to exceed the statements for controversial, preferred size). The fixed size pool is generally considered to be the better choice. A time-based expiration strategy is article, appropriate for statements issues, most types of cache elements. The timestamp strategy is: Timestamp the objects; Update the time stamp when you use the objects or refresh the information; Throw away objects whose timestamps have expired. Only data that must be always totally up to copy essay without date cannot effectively use a time-based expiration strategy. Thesis Issues? [Article discusses and implements a time-based expiration framework]. J2ME game building (Page last updated April 2002, Added 2002-05-19, Author Dale Crowley, Publisher DevX). Tips: J2ME device memory and speeds are very limited which affects everything from the data-loading speed to the frame/refresh rate, and critiquing article seriously limits the ability to animate characters or otherwise rapidly change the screen. Smart graphics is important: you need to draw clear, concise images at extremely low resolutions and with very small palettes. Animated characters need dynamic, easily-read poses which avoid kicks looking like a dance steps, or punches looking like an arm waves.
Use public variables in your classes, rather than using accessors. This is technically bad programming practice but it saves bytecode space. Be extra careful to thesis place things in without memory only when they are in use. For example, discard an introduction splash screen after display. Try to reduce the number of classes used. Combine classes into one if they vary only slightly in behavior. Every class adds size overheads. Remember that loading and installing applications into J2ME phones is a relatively slow process. Sun community chat on High Performance GUIs with the statements for controversial issues, JFC/Swing, with Steve Wilson, Scott Violet, and Chet Haase (Page last updated April 2002, Added 2002-05-19, Author Edward Ort, Publisher Sun). Without? Tips: [Some discussion of performance improvents in 1.4] Multi-threading with swing must be done correctly, using invokeAndWait() and invokeLater().
Default models have performance limitations. Create dedicated models for high performance. Consider using a custom RepaintManager for very large tables. Don't use a MouseListener with a renderer BufferedImage is treated more optimally than MemoryImageSource Try using createImage(w,h), which returns an image in the same format as the screen, which allows faster copies from that image to issues the screen (important for copying speed issues). LinkedHashMap and RandomAccess (Page last updated July 2002, Added 2002-07-24, Author Glen McCluskey, Publisher Sun). Tips: LinkedHashMap preserves various ordering information, optionally including access ordering which makes LinkedHashMap appropriate for a least recently used (LRU) cache. Copy Essay Without? ArrayList has fast random access of thesis statements for controversial issues, elements, LinkedList has slow random access of elements.
List classes that implement the RandomAccess interface have fast random access and using get() to iterate their elements is scholarship application without essays, efficient. If RandomAccess is not implemented, use an Iterator to thesis statements issues iterate the elements. Data expiration in caches (Page last updated January 2002, Added 2002-02-22, Author William Grosso, Publisher OnJava). Scholarship Application Without Essays? Tips: [Article discusses and implements a framework for a cache with built in element expiration handling]. Emulating another system (a ZX Spectrum) (Page last updated July 2002, Added 2002-07-24, Author Razvan Surdulescu, Publisher Java Developers Journal).
Tips: Painting pixel by pixel by repeatedly calling fillRect() is thesis, slow. Instead create the offscreen image as a decorator for a java.awt.image.MemoryImageSource object containing a byte array in RGB format with the pixel data. The rendering code updates the byte array and then calls MemoryImage-Source.newPixels() to article notify the object that the data has been updated. Pre-render common images or pixel combination, retain them as Image objects and thesis statements use java.awt.Graphics.drawImage() (Java 1) or java.awt.image.BufferedImage.setRGB() (Java 2) to of christmas render the image to the graphics buffer. Report of how Ace's Hardware made their SPECmine tool blazingly fast (Page last updated December 2001, Added 2002-02-22, Author Chris Rijk, Publisher Ace's Hardware). Tips: Tranform your data to minimize the costs of searching it. Thesis Statements? If your dataset is small enough, read it all into on child in india memory or use an in-memory database (keeping the primary copy on disk for recovery). An in-memory datavase avoids the following overheads: no need to pass data in from a separate process; less memory allocation by avoiding all the data copies as it's passed between processes and layers; no need for data conversion; fine-tuned sorting and filtering possible; other optimizations become simpler. Pre-calculation makes some results faster by making the database data more efficient to access (by ordering it in advance for example), or by setting up extra data in advance, generated from the main data, to make calculating the results for a query simpler.
Pre-determine possible data values in thesis queries, and use boolean arrays to access the chosen values. Pre-calculate all formatting that is invariant for generated HTML pages. Cache all reused HTML fragments. Write Unit? Caching many strings may consume too much memory. IF memory is limited, it may be more effective to generate strings as needed. Write out strings individually, rather than concatenating them and writing the result. Thesis Issues? Extract common strings into an identical string object.
Compress generated html pages to how to unit send to the user, if their browser supports compressed html. This is a heavier load on the server, but produces a significantly faster transfer for limited bandwidth clients. Statements? Some pages are temporarily static. Cache these pages, and only re-generate them when they change. Caching can significantly improve the essays article, responsiveness of a website. Email summarizing best practices for Promoting Scalable Web Services (Page last updated January 2002, Added 2002-02-22, Author Roger L. Costello, Publisher Costello).
Tips: Web services best practices are mainly the same as guidelines for developing other distributed systems. Stay away from using XML messaging to do fine-grained RPC, e.g. a service that returns a single stock quote (amusingly this is the classic-cited example of a Web service). Do use course-grained RPC, that is, use Web services that do a lot of work, and return a lot of information. When the transport may be slow and/or unreliable, or the processing is complex and/or long-running, consider an thesis for controversial asynchronous messaging model. Always take the overall system performance into on summer vacation 7 account. Thesis Statements For Controversial? Don't optimize until you know where the bottlenecks are, i.e., don't assume that XML's bloat or HTTP's limitations are a problem until they are demonstrated in your application. Take the frequency of the thesis rights, messaging into account. Replicate data as necessary. For aggregation services, try to retrieve data during off-hours in large, course-grained transactions. Caching SOAP services (Page last updated March 2002, Added 2002-03-25, Author Ozakil Azim and Araf Karsh Hamid, Publisher JavaWorld). Thesis Statements For Controversial Issues? Tips: Repeated SOAP-client calls to access server state can choke a network and degrade the server performance.
Cache data on the client whenever possible to avoid requests to the server. Ensure the client data remains up to date by using a call to a server service which blocks until data is changed. String concatenation, and IO performance. (Page last updated March 2002, Added 2002-03-25, Author Glen McCluskey, Publisher Sun). Tips: String concatenation '+' is implemented by the Sun compiler using StringBuffer, but each concatenation creates a new StringBuffer so is scholarship application without, inefficient for multiple concatenations. Immutable objects should cache their string value since it cannot change. Operating systems can keep files in their own file cache in thesis statements for controversial memory, and accessing such a memory-cached file is much faster than accessing from disk.
Be careful of this effect when making I/O measurements in performance tests. Fragmented files have a higher disk access overhead because each disk seek to find another file fragment takes 10-15 milliseconds. Keep files open if they need to application essays be repeatedly accessed, rather than repeatedly opening and closing them. Use buffering when accessing file contents. Explicit buffering (reading data into an array) gives you direct access to the array of data which lets you iterate over the elements more quickly than using a buffered wrapper class. Counting lines can be done faster using explicit buffering (rather than the readLine() method), but requires line-endings to thesis statements be explicitly identified rather than relying on essay on summer 7 the library method determining line-endings system independently. Sun community chat on EJBs with Pravin Tulachan (Page last updated March 2002, Added 2002-03-25, Author Edward Ort, Publisher Sun). Tips: CMP (container managed persistence) is generally faster than BMP (bean managed persistence).
BMP can be faster with proprietary back-ends; with fine-grained transaction or security requirements; or to for controversial issues gain complete detailed persistency control. Scalability is improved by passing primary keys rather than passing the entities across the network. How To? EJB 2.0 CMP is far faster than EJB 1.1 CMP. EJB 1.1 CMP was not necessarily capable of scaling to high transaction volumes. If EJBs provide insufficient performance, session beans should be used in thesis for controversial issues preference. Don't make fine-grained method calls across the essays, network. For Controversial? Use value object and session facade design patterns instead. Multithreading and read-write locks (Page last updated January 2002, Added 2002-01-25, Author Nasir Khan, Publisher EarthWeb).
Tips: When a thread passes through a synchronized block, all variables throughout the thread are synchronized with main memory, not just the set of variables in the current method. Multithreading and read-write locks, part 2 (Page last updated January 2002, Added 2002-01-25, Author Nasir Khan, Publisher EarthWeb). Tips: Operations on how to write unit primitive variables are atomic (except double and long), but a combination of two atomic operations is not atomic, and it is easy to make a mistake about this. Statements? Volatile variables are always synchronized with the main memory copy. Hotspot garbage collection in detail (Page last updated January 2002, Added 2002-01-25, Author Ken Gottry, Publisher JavaWorld). Tips: HotSpot garbage collection default parameters are effective for most small applications, but can be tuned to improve throughput for large, server-side applications. The most straightforward garbage collection algorithms iterate over every reachable object: this takes an amount of time proportional to the number of living objects.
Throughput (the percentage of total time not spent in GC) is normally the relevant metric for a server process since GC pauses may be tolerable or simply obscured by network latency. Pauses (the times during GC when an application is essays article, unresponsive) is the more relevant metric for interactive graphical programs and thesis statements issues other programs where short pauses may upset the user experience. On systems with limited physical memory, footprint (the working set of a process, usually measured in pages) may dictate scalability. [Article dicusses various parameters available to essays article tuning HotSpot heap space]. Use verbosegc to for controversial issues capture garbage collection statistics. Quality of service for web services (Page last updated January 2002, Added 2002-02-22, Author Anbazhagan Mani, Arun Nagarajan, Publisher IBM). Tips: Quality of service requirements for thesis on child rights, web services are: availability (is it running); accessiblity (can I run it now); integrity/reliability (will it crash while I run/how often); throughput (how many simultaneous requests can I run); latency (response time); regulatory (conformance to standards); security (confidentiality, authentication). HTTP is a best-effort delivery service. Thesis Statements For Controversial Issues? This means any request could simply be dropped. Web services have to handle this and retry.
Web service latencies are measured in the tens to thousands of milliseconds. Asynchronous messaging can improve throughput, at the cost of latency. SOAP overheads include: extracting the SOAP envelope; parsing the essay on summer 7, contained XML information; XML data cannot be optimized very much; SOAP requires typing information in thesis statements every SOAP message; binary data gets expanded (by an write average of thesis statements for controversial issues, 5-fold) when included in XML, and also requires encoding/decoding. Application Essays? Most existing XML parsers support type checking and conversion, wellformedness checking, or ambiguity resolution, making them slower than optimal. Consider using of thesis for controversial issues, stripped down XML parser which only pe4rforms essential parsing. Thesis On Child Rights In India? DOM based parsers are slower than SAX based ones. Compress the thesis statements for controversial, XML when the how to unit, CPU overhead required for compression is less than the network latency.
Other factors affecting web service performance are: web server response time and availability; web application execution time (like EJB/Servlets in Web application server); back-end database or legacy system performance. Requests results should be cached where possible. Requests should be load balanced, prioritized according to the business value it represents. For Controversial Issues? Carry out capacity planning to enable the performance to essays be maintained in the future. Extreme care should be taken to make sure that resources are not locked for thesis for controversial, long periods of time, to avoid serious scalability problems. Measure the performance of essays of christmas, your web services by adding code measuring elapsed time to the generated service proxy (and recompiling). Thesis Statements For Controversial? [Article gives an example]. Object Resource Pooling (Page last updated March 2002, Added 2002-03-25, Author Paul King, Publisher OCI). Scholarship Application? Tips: If the overhead associated with creating a sharable resource is expensive, that resource is a good candidate for pooling. Pooled objects create a resource in advance and store it away so it can be reused over-and-over. Thesis For Controversial Issues? Pooling may be necessary if a limited number of without, shared resources are available. Thesis Statements For Controversial? Pooling supports strategies such as load balancing, all-resources-busy situations, and other policies to optimize resource utilization. [Article discusses pooling characteristics].
Load balancing is thesis in india, possible by varying how pooled objects are handed out. Pool size can be tuned using low-water and high-water marks. Waiting time when accessing empty pools can be tuned using a timeout parameter. Unusable pooled objects may be recovered when most efficient, not necessarily when the underlying resource fails. The Recycler pattern fixes only the broken parts of statements for controversial issues, a failed object, to minimize the replacement cost.
Using NIO (Page last updated March 2002, Added 2002-03-25, Author Aruna Kalagnanam and Balu G., Publisher IBM). Tips: A server that caters to hundreds of essay vacation 7, clients simultaneously must be able to use I/O services concurrently. Prior to 1.4, an almost one-to-one ratio of threads to clients made servers written in Java susceptible to enormous thread overhead, resulting in both performance problems and for controversial issues lack of scalability. The Reactor design pattern demultiplexes events and dispatches them to thesis registered object handlers. (The Observer pattern is similar, but handles only a single source of events where the Reactor pattern handles multiple event sources). [Articles covers the changes needed to use java.nio to make a server efficiently muliplex non-blocking I/O from SDK 1.4]. J2EE best practices. Thesis For Controversial Issues? (Page last updated February 2002, Added 2002-03-25, Author Chris Peltz, Publisher HP). Without? Tips: Executing a search against the database calls one of the finder() methods. Thesis For Controversial? finder() methods must return a collection of remote interfaces, not ValueObjects. Consequently the client would need to essays critiquing make a separate remote call for each remote interface received, to acquire data. The SessionFacade pattern suggests using a session bean to encapsulate the query and thesis for controversial return a collection of ValueObjects, thus making the request a single transfer each way.
The Value Object Assembler pattern uses a Session EJB to aggregate all required data as various types of write, ValueObjects. For Controversial Issues? This pattern is used to application satisfy one or more queries a client might need to statements for controversial execute in order to essay vacation for class 7 display multiple data types. MIDP GUI programming (Page last updated March 2002, Added 2002-03-25, Author Qusay Mahmoud, Publisher OnJava). Tips: Applications with high screen performance needs, like games, need finer control over MIDP screens and should use the javax.microedition.lcdui package which provides the low-level API for for controversial issues, handling such cases. Always check the drawing area dimensions using Canvas.getHeight() and Canvas.getWidth() [so that you don't draw unnecessarily off screen]. Essays Critiquing? Not all devices support color. Thesis Statements For Controversial Issues? Use Display.isColor() and Display.numColors( ) to determine color support and avoid color mapping [overheads].
Double buffering is possible by using an offscreen Image the size of the screen. How To Unit? Creating the image: i = Image.createImage(width, height); Getting the Graphics context for drawing: i.getGraphics(); Copying to the screen g.drawImage(i, 0, 0, 0); Check with Canvas.isDoubleBuffered(), and thesis issues don't double-buffer if the MIDP implementation already does it for you. To avoid deadlock paint() should not synchronize on how to any object already locked when serviceRepaints() is for controversial issues, called. Entering alphanumeric data through a handheld device can be tedious. If possible, provide a list of choices from which the user can select. Article on essay without the cost of thesis for controversial issues, casts (Page last updated December 1999, Added 2000-12-20, Author Dennis M. Sosnoski, Publisher JavaWorld). Tips: Casting can be detrimental to performance. Improve performance by minimizing casting in heavily used code. Some casts take nearly as long as a simple object allocation. [Article discusses various ways of avoiding casts, showing advantages and drawbacks.] Article on Java 2 collections (Page last updated , Added 2000-12-20, Author Dennis M. Sosnoski, Publisher JavaWorld). Tips: Convert collections into arrays for improved access speed.
The conversion can be made slightly faster by implementing it in a subclass so that collection element access can avoid access methods, accessing elements directly. Customized implementations of Hashtables can perform better. Use type specific implementations of collections for better performance (e.g. IntegerVector rather than Vector) [Article describes a type-generic base class for typed arrayed collections.] Scaling SOAP-based web services. On Child Rights? (Page last updated November 2001, Added 2001-11-27, Author Frank Cohen, Publisher IBM). Tips: Cache the statements for controversial issues, web services description language (WSDL) in a centralized database and periodically check for newer versions. Cache schema definitions for scalability. Use simple SOAP data types (String, Int, Float, NegativeInteger).
Each new data type introduces a serializer to convert from the XML value into a Java value and back again, which may cause performance problems. How To? SOAP messages move much more data than the average HTTP GET or POST call, adversely impacting network performance. Transactional SOAP calls need to thesis for controversial issues cache the state of sessions. [Article dicusses a free open-source utility called Load to stress test SOAP-based web services]. Rules and Patterns for Session Facades (Page last updated June 2001, Added 2001-07-20, Author Kyle Brown, Publisher IBM). Tips: Use the Facade pattern, and specifically Value objects, to transfer all the subset of data needed from an entity bean in one transfer. EJBs are wonderful (Page last updated December 2001, Added 2001-12-26, Author Tyler Jewell, Publisher OnJava). Tips: The out-of-the-box configuration for Entity EJB engines, such as WebLogic, are designed to handle read-write transactional data with the best possible performance. There are studies that demonstrate entity EJBs with CMP have lackluster performance when compared with a stateless session bean (SLSB) with JDBC. [Author points out however that SLSB/JDBC combination is essay for class 7, less robust, less configurable, and less maintainable]. Configure separate deployments for each entity bean for different usage patterns (e.g. typical 85% read-only, 10% read-write, 5% batch update), and partition the presentation layer to use the statements issues, appropriate corresponding deployment (e.g. Essay Without? read requests use the read-only deployment).
EJB performance tips (Page last updated December 2001, Added 2001-12-26, Author Krishna Kothapalli and Raghava Kothapalli, Publisher JavaPro). Tips: Design coarse-grained EJB remote interfaces to reduce the number of network calls required. Statements For Controversial? Combine remote method calls into one call, and combine the data required for the calls into essays critiquing one transfer. Reduce the number of JNDI lookups: cache the home handles. Use session bean wrapper for returning multiple data rows from an entity bean, rather than returning one row at a time. Use session beans for thesis for controversial, database batch operations, entity beans typically operate only one row at scholarship essays a time. Thesis Statements? Use container-managed persistence (CMP) rather than bean-managed persistence (BMP). Essay On Summer Vacation For Class? Use entity beans when only for controversial issues, a few rows are required for article, the entity, and when rows need to be frequently updated. Thesis Issues? Use the lowest impact isolation (transaction) level consistent with maintaining data coherency. Highest impact down: TRANSACTION_SERIALIZABLE, TRANSACTION_REPEATABLE_READ, TRANSACTION_READ_COMMITED, TRANSACTION_READ_UNCOMMITED. Correctly simulate the production environment to tune the application, and use profiling and essay on summer for class 7 other monitroing tools to identify bottlenecks.
Tune the underlying system, e.g. TCP/IP parameters, file limits, connection pool parameters, EJB pools sizes, thread counts, number of JVMs, JVM heap size, shared pool sizes, buffer sizes, indexes, SQL queries, keep/alive parameters, connection backlogs. For Controversial? Use clustering to meet higher loads or consider upgrading the hardware. Both Java specific and Java on OS/390 tips. Essays Critiquing? (Page last updated 2000, Added 2000-10-23, Author ?, Publisher IBM). Thesis For Controversial? Tips: Use the scholarship application without essays, latest release of the statements, SDK. Use zip and jar files.
Partition classes to different zip/jar files according to usage. Order the entries in CLASSPATH so that classes are found quickly (the default classloaders do a linear search in essays each entry's directory or zip/jar file). If using a large number of threads (thousands) tune the underlying OS to thesis for controversial support this. Vary the -ss parameter to optimize for threads. Threads generally don't need more than 256K stack size. Minimize the essay, number of JNI calls Use primitive types for variables Avoid excessive writing to the Java console Use synchronized methods only when necessary Cache/reuse frequently used objects when possible Declare methods as final [dubious tip].
Use static final when creating constants Use int instead of long. Use local variables in preference to class and issues instance variables. Use arrays instead of rights in india, vectors Consider when to use a temporary variable to manipulate class and instance variables in loops (speed vs. memory) Add and delete items from the issues, end of a vector Avoid unnecessary cast and instanceof Avoid using String when doing a lot of how to write unit, character manipulation. Thesis Statements For Controversial Issues? Use StringBuffer instead. Application Without Essays? Avoid using long divides. Javaworld tip article, detailing a buffered RandomAccessFile class. (Page last updated 1998?, Added 2000-10-23, Author Nick Zhang). Unfortunately the getNextLine() is too system specific - don't forget systems where lines are 'r' terminated. Tips: Use buffered i/o classes. Re-implement classes to avoid synchronization, where this is applicable. RMI performance tuning (Page last updated September 2001, Added 2001-10-22, Author Ashok Mathew and Mark Roulo, Publisher JavaWorld).
Tips: Use netperf to measure network bandwidth. Consider altering the statements, TcpWindowSize parameter. Configure RMI garbage collection by setting the properties sun.rmi.dgc.client.gcInterval and sun.rmi.dgc.server.gcInterval . Send groups of objects together rather than one object at a time. Without? Implementing Externalize can speed up transfers. Issues? Pack data to reduce the number and amount of reads and writes, and scholarship application without essays the amount of data transferred. Have object directly serialize contained objects or tell those objects to for controversial issues serialize themselves using Externalize methods (i.e. Of Christmas? chain Externalize methods for all contained objects). Use special codes to handle special cases such as singleton or reusable objects. Don't introduce extra complications once performance targets have been met.
Local entity beans (Page last updated October 2001, Added 2001-10-22, Author Alex Pestrikov, Publisher Java Developers Journal). Tips: Local entity beans do not need to be marshalled, and thesis do not incur any marshalling overhead for method calls either: parameters are passed by scholarship application essays reference. Local entity beans are an optimization for for controversial issues, beans which it is known will be on the same JVM with their callers. Facade objects (wrappers) allow local entity beans to be called remotely. Of Christmas? This pattern incurs very little overhead for for controversial issues, remote calls, while at the same time optimizing local calls between local beans which can use local calls. Nice article on understanding bytecodes by Peter Haggar, Added 2000-10-23, Author of Practical Java. Explains why a synchronized method is faster than a functionally identical synchronized block. (Page last updated 2000, Added 2000-10-23, Author Peter Haggar, Publisher IBM).
Tips: Understanding bytecodes can help determine how to improve performance. Critiquing Article? It can also help you to create smaller sized class files. Thesis For Controversial Issues? Don't synchronize code unless synchronization is required. Use synchronized methods rather than synchronized blocks where the code would be functionally identical. Essays? The -O option in statements issues SDK 1.2 does nothing. Use the -g:none option to make files class smaller [or use a better optimizing compiler] Move invariants out of loops. Apply simple optimizations like loop unrolling, algebraic simplification, and strength reduction by hand. Chapter 1 of copy essay without, Enterprise Java Performance, Performance in General. Includes the infamous sentences It is likely that the code will not meet the thesis statements issues, performance requirements the very first time it runs.
Even if it does, it may be worthwhile to look for some ways to improve it. NO NO NO! If the code meets the performance requirements, DON'T CHANGE IT. Next time guys, ask me to review your book before you publish. (Page last updated 2000, Added 2000-10-23, Authors Steven Halter Steven Munroe, Publisher Sun). Tips: The simplest code usually performs best. Consider performance requirements before coding. Application Without Essays? Write reasonable code without worrying too much about performance until later. If the design identifies a critical section of thesis issues, code, spend time considering that code's performance before and while writing it. Define performance requirements explicitly. Redefine fuzzy requirements to be more explicit. The target machine affects performance requirements.
Use the simplest classes possible--but no simpler. [Don'cha just love it. And here I was using classes simpler than is possible. Gotta make 'em more complex now.] Don?t recalculate things that are constant in loops. Reuse objects where possible. Choose the correct collection for scholarship, performance. Use the default Java data values where possible to avoid reassigning them. Use raw arrays in issues preference to collections. Performance fixing is iterative. Essays Of Christmas? Fixing one bottleneck often reveals another previously hidden one.
Keep performance in mind during the design phase. Avoid monopolizing shared resources. Design is important for thesis, any distributed parts of of christmas, a distributed application. The real performance limitations are physical limitations: bandwidth, communication distance, access speed, unavoidable overheads, resource limitations, etc. Thesis Statements Issues? JNI calls are not necessarily faster than using pure Java because of JNI overheads.
Schema mapping is complex. [Buy a product that does it for you.] Chapter 4 of on summer 7, Enterprise Java Performance, Local/Remote Issues. (Page last updated 2000, Added 2000-10-23, Authors Steven Halter Steven Munroe, Publisher Sun). Tips: RMI over IIOP has a higher overhead than plain RMI. Objects that can be configured to be local or remote at any time, provides the flexibility to optimize performance. Large grained remote calls [i.e. batched calls] perform better than small grained remote calls [lots of little calls]. Thesis Statements For Controversial? Persistency adds overheads that make persistent objects slower. Instead of serializing the transitive closure (recursive traversal of all objects referenced), break up objects into smaller chunks. Use stubs, proxies and handles [essentially objects that indirectly refer to other objects] to essay on summer 7 break up serialization into statements issues smaller chunks. Unless the application is put together with care, the remote method call costs may dominate. Group objects that interact strongly [a lot] in of christmas the same physical location.
The closer they are, the more efficient their interaction. Cache in the client any read-only objects, for the whole session. Replicate any data needed so that queries run locally in the client. Written objects can be held in the client and periodically written to the server, rather than updating the server object on each change. For Controversial? Good partitioning of objects in essay for class distributed applications limits interactions between objects in different partitions and takes advantage of local method access for objects within each partition.
Application partitioning is best addressed early in thesis statements for controversial the design. How to use java.rmi.MarshalledObject (Page last updated March 2001, Added 2001-04-20, Author Stuart Halloway, Publisher Sun). Scholarship? Tips: MarshalledObject lets you postpone deserializing objects. Thesis Statements For Controversial Issues? This lets you pass an object through multiple serialization/deserialization layers (e.g. passing an object through many JVMs), without incurring the serialization/deserialization overheads until absolutely necessary. Doug Bell's article with various low-level techniques and benchmark applets. (Page last updated 1997, Added 2000-10-23, Author Doug Bell, Publisher JavaWorld). Tips: Don't optimize unless necessary. Critiquing Article? Optimizing can: introduce new bugs; make code harder to thesis for controversial issues understand and copy essay without maintain; reduce the extensibility of the code. 90 percent of a program's excution time is spent executing 10 percent of the code. (Some people use the 80 percent/20 percent rule).
Optimizing the other 90 percent of the program (where 10 percent of the execution time was spent) has no noticeable effect on performance. General optimization techniques include: strength reduction; common sub expression elimination; code motion; unrolling loops. Use compiler features: constant folding; branch folding; dead code elimination. For Controversial? Use the thesis on child rights in india, -O option (javac -O). Use a profiler to identify bottlenecks. Always time the code before and after making changes to verify that, at for controversial least on the test platform, your changes improved the program.
Try to essays of christmas make each timing test under identical conditions. If possible, contrive a test that doesn't rely on any user input, as the variations in user response can cause the results to for controversial issues fluctuate. Tuning the IBM JVM and Linux (Page last updated May 2001, Added 2001-10-22, Authors Duc Vianney and James Phelan, Publisher IBM). Tips: [Article also has detailed coverage of tuning Linux]. Use the essay without, -Xms and -Xmx parameters to statements issues set the heap size. Use -verbosegc to thesis on child rights measure garbage collection statistics. Keep heap size smaller than physical memory. Keep heap size small enough that all other necessary processes also fit into physical memory. Thesis Statements For Controversial? The IBM JVM has extra options to control JVM Focus initially on design, data structures, and algorithms. Do not rely on compile-time code optimization.
Understand runtime code optimization. Use StringBuffer, rather than String, for concatenation. Minimize the cost of object creation. Guard against unused objects. Essay On Summer? Minimize synchronization.
Use stack variables whenever possible. Use static, final, and private methods to allow inlining. Initialize instance variables only thesis, once. Use primitive types for faster and copy essay smaller code. Do not use an Enumeration or an Iterator to traverse a Vector. Use System.arraycopy for statements for controversial issues, copying arrays. Prefer an array to a Vector or ArrayList. Reuse objects whenever possible.
Use lazy evaluation. Optimize source code by hand. Compile to native code. Performance tuning embedded Java (Page last updated August 2001, Added 2001-08-20, Author Vincent Perrier, Publisher OnJava). Critiquing Article? Tips: All the following affect embedded Java performance: hardware processor selection; (real-time) operating system selection; supported Java APIs; application reliability and scalability; graphics support; and the ability to put the application code into ROM. Statements For Controversial? Various approaches for essay, boosting bytecode execution speed include: a JIT compiler (usually too big for thesis statements for controversial issues, embedded systems); an ahead-of-time compiler (requires more ROM, may disallow or slowdown dynamically loaded classes); a dynamic adaptive compiler (half-way house between last two options); putting the Java application code into ROM; rewriting the JVM interpretation loop in assembly; using a Java hardware accelerator. Use the lightweight graphical toolkit. How To Unit? To keep down the memory footprint, eliminate any classes that are not used (java -v lists all classes as they are loaded), and run in interpreted mode as much as possible. Benchmark results are not necessarily applicable to your application [article reviews the applicability of standard and thesis proprietary benchmarks]. Caching (Page last updated July 2001, Added 2001-08-20, Author Jonathan Lurie, Publisher JavaWorld). Tips: Nice description of caching using a filing system analogy.
Nice introductory description of implementating caching, and of managing caching overheads and element expiration. J2EE challenges (Page last updated June 2001, Added 2001-07-20, Author Chris Kampmeier, Publisher Java Developers Journal). Tips: Thoroughly test any framework in a production-like environment to ensure that stability and performance requirements are met. Each component should be thoroughly reviewed and tested for how to write unit, its performance and security characteristics. Using the underlying EJB container to manage complex aspects such as transactions, security, and remote communication comes with the price of additional processing overhead. To ensure good performance use experienced J2EE builders and thesis for controversial issues use proven design patterns.
Consider the article, impact of session size on performance. Avoid the following common mistakes: Failure to close JDBC result sets, statements, and connections; Failure to thesis statements remove unused stateful session beans; Failure to invalidate HttpSession. Performance test various options, for example, test both Type 2 and Type 4 JDBC drivers; Use a load-generation tool to simulate moderate loads; monitor the server to identify resource utlization. Perform code analysis and profiling. Performance requirements include: the required response times for end users; the perceived steady state and peak user loads; the average and peak amount of data transferred per Web request; the expected growth in user load over the next 12 months. Note that peak user loads are the number of concurrent sessions being managed by the application server, not the number of rights in india, possible users using the system. Larger loads require greater amounts of statements, hardware to essays satisfy that load. Applications that perform very little work can typically handle many users for a given amount of hardware, but can scale poorly as they spend a large percentage of time waiting for shared resources. Applications that perform a great number of computations tend to thesis statements require much more hardware per user, but can scale much better than those performing a small number of computations.
Processor integer performance is usually the most important hardware factor, though a server can scale poorly if shared resources cause significant contention. Cache design and how to write memory bandwidth play a big role in statements determining how much extra performance is essays of christmas, achieved, as processors are added to statements issues a server. Additional capacity should be designed into the system. Extrapolate from known performance test results to essay on summer vacation for class 7 predict the performance of the system when varying amount of resources are available. EJB Clustering (Page last updated February 2002, Added 2002-04-26, Author Tyler Jewell, Publisher BEA).
Tips: Four locations that can provide clustering logic for thesis statements issues, an EJB are: the for class 7, JNDI naming server where the home stub is thesis for controversial issues, bound, the scholarship without, container, the home stub, and the remote stub. J2EE Application servers (Page last updated April 2001, Added 2001-04-20, Authors Christopher G. Statements Issues? Chelliah and scholarship Sudhakar Ramakrishnan, Publisher Java Developers Journal). Tips: A scalable server application probably needs to be balanced across multiple JVMs (possibly pseudo-JVMs, i.e. multiple logical JVMs running in the same process). Performance of an application server hinges on caching, load balancing, fault tolerance, and clustering. Application server caching should include web-page caches and data access caches. Other caches include caching servers which guard the application server, intercepting requests and either returning those that do not need to go to the server, or rejecting or delaying those that may overload the app server. Application servers should use connection pooling and database caching to minimize connection overheads and round-trips. Statements For Controversial? Load balancing mechanisms include: round-robin DNS (alternating different IP-addresses assigned to a server name); and of christmas re-routing mechanisms to statements issues distribute requests across multiple servers. How To? By maintaining multiple re-routing servers and a client connection mechanism that automatically checks for an available re-routing server, fault tolerance is added. Using one thread per user can become a bottleneck if there are a large number of concurrent users. Distributed components should consider the proximity of components to their data (i.e., avoid network round-trips) and how to distribute any resource bottlenecks (i.e., CPU, memory, I/O) across the different nodes.
Hans Bergsten's top ten JSP tips (Page last updated November 2000, Added 2001-01-19, Author Hans Bergsten, Publisher O'Reilly). Tips: The include directive (%@ include file=filename.inc %) is faster than the include action (jsp:include page=pagename.jsp flush=true/). redirect s are slower than forward s because the thesis statements for controversial issues, browser has to make a new request. Database access is typically very expensive in terms of server resources. Use a connection pool to share database connections efficiently between all requests, but don't use the JDBC ResultSet object itself as the cache object. The Optimistic Locking pattern (Page last updated July 2001, Added 2001-07-20, Author Yasmin Akbar-Husain and Eoin Lane, Publisher JavaWorld).
Tips: Pessimistic locking, where database data is locked when read, can lead to essay on summer vacation high lock contention. Optimistic locking only thesis issues, checks data integrity at update time, so has no lock contention [but can have high rollback costs]. This is Optimistic Locking pattern is usually more scalable than pessimistic locking. Detection of write-write conflicts with optimistic transactions can be done using timestamps or version counts or state comparisons. Reusing objects in embedded Java (Page last updated July 2001, Added 2001-07-20, Author Angus Muir and Roman Bialach, Publisher Micro Java). Essays Of Christmas? Tips: A lot of object creation and destruction can lead to statements for controversial issues a fragmented heap, which reduces the ability to create further objects.
Define the bulk of memory you need (buffers, etc.) up-front at initialization, and use object pooling to avoid further creation or destruction of objects. Throwing/catching exceptions are tremendously expensive. Pooling is not always faster than object creation. Object recycling part 2 (Page last updated February 2002, Added 2002-02-22, Author Angus Muir and Roman Bialach, Publisher Micro Java). Tips: The efficiency of pooling objects compared to copy essay without creating and disposing of objects is highly dependent on the size and complexity of the objects. Object pools have deterministic access and reclamation costs for thesis statements, both CPU and memory, whereas object creation and garbage collection can be less deterministic. Chapter 2, Java: Fat and essay without Slow?, of thesis statements for controversial issues, Java 2 Micro Edition: Professional Developer's Guide referenced from thesis on child in india http://www.microjava.com/articles/techtalk/giguere(Page last updated May 2001, Added 2001-07-20, Author Eric Giguere, Publisher Micro Java). Tips: Reduce compiled code size by using implicit instruction bytcodes wherever possible.
For example, limiting a method to four or fewer local variables (three on non-static methods as this takes the first slot), allows the statements for controversial, compiler to use implicit forms of instructions (such as aload, iload, fload, astore, istore, fstore, and so on). Similarly numbers -1, 0, 1, 2, 3, 4 ,5 have special bytecodes Java class files are standalone - no data is shared between class files. In particular strings are repeated across different files (one reason why they compress so well when packaged together in write unit JAR files). An empty class compiles to thesis statements issues about 200 bytes, of which only 5 bytes are bytecode. There are no instructions for initializing complete arrays in the Java VM. Instead, compilers must generate a series of bytecodes that initialize the array element by element. This can make array initialization slow, and adds bytecode to the class. You can reduce bytecode bloat from array initialization by encoded values in strings and using those strings initialize the arrays.
Explicitly set references to null when they are no longer needed to without ensure that the objects can be garbage collected. Allocate objects less often and allocate smaller objects to reduce garbage collection frequency. Animation in java applets article. Old article, but basically sound (the basics haven't changed). (Page last updated March 1996, Added 2000-12-20, Authors Arthur van Hoff and thesis statements for controversial Kathy Walrath, Publisher JavaWorld). Tips: Use a separate thread to draw the animation. Do not use the paint() method. Unit? Destroy the animation drawing thread when the user leaves the page (Applet.stop() is called) to thesis statements for controversial avoid consuming CPU when nothing is being viewed. Keep the correct frame rate by calculating elapsed time and delaying for the remaining time, rather than always simply delaying for scholarship without, a contant time period.
Override the thesis statements for controversial issues, update() method to essay on summer for class avoid flashing (update() clears the frame each time it is thesis, painted). Use double buffering to eliminate further flashing and usually faster drawing: drawing offscreen is potentially faster, and write unit mapping blocks of statements for controversial, pixels oto the screen is normally very fast. On Summer For Class? Use a media tracker class to avoid displaying images until they are fully loaded. [This still applies, but Java 2 has more interfaces to help you do this.] Use image strips to load multiple images in thesis statements issues one action. Inter-frame compression can reduce the total size of multiple images of an how to unit animation, and so improve animation network/disk transfer rates. Another tutorial from Sun. This ones on statements for controversial animation (Page last updated ?, Added 2000-12-20, Author ?, Publisher Sun). Tips: Normal frame rates for animation: 8 frames per second (fps) for copy without, poor quality animation; 12 fps for standard animation; 24 fps for short bursts of smooth, realistic motion. Animation loop (usually a separate thread) keeps track of frames and thesis statements for controversial issues requests screen updates. Suspend the animation whenever it is not visible. Use the thesis on child in india, MediaTracker to load all required images before drawing, using checkID(anInt, true)/checkAll(true) [asynchronously] or waitForID()/waitForAll() [synchronous]. [example code included in article] Combine images in a single file (e.g. jar file, or single image strip) to statements issues improve image loading if transferring them over a network. Basic animation tutorial (Page last updated ?, Added 2000-12-20, Author Dave ?, Publisher ?).
Tips: Avoid flicker by overriding the update() method to copy avoid blanking the thesis for controversial, canvas. Use a separate thread to manage the calculations and drawing. Use MediaTracker to load all required images before drawing. Use double buffering (draw image on essay on summer for class 7 offscreen buffer, then map onto thesis statements screen buffer). Essay Without? Use synchronization to synchronize methods in the two threads. Moving from JSP to EJB (Page last updated June 2001, Added 2001-06-18, Author Patrick Sean Neville, Publisher Java Developers Journal). For Controversial? Tips: Entity EJBs should contain aggregate get/set methods that return chunks of data rather than fine-grained get/set methods for individual attributes, to reduce unnecessary database, transactional, and network communication overheads. Avoid stateful session beans as they are resource-heavy, since one instance is maintained for each client. Scholarship Essays? Under heavy loads, entity beans should do more than merely represent a table in a database.
If you are merely retrieving and issues updating data values, consider using JDBC within session beans instead. If you have one large database host but only a small Web and middleware host, consider moving much of your logic into stored procedures and calling them via JDBC in session beans. If your database host is weak or unknown, or you require greater portability, keep the data calculations in entity beans. Essays? Consider using a single stateless session bean to provide access to other EJBs (this is a fa?ade pattern). This optimizes multiple EJB references and statements for controversial issues calls by keeping them in-process. Container Managed Persistence (CMP) typically provides better performance (due to data caching) than Bean Managed Persistence (BMP). Judging various aspects of Java, including performance (Page last updated May 2001, Added 2001-06-18, Author Brian Maso, Publisher DevX). Essays Of Christmas? Tips: J2EE defines component models with high scalability potential.
Maximizing scalability requires sticking to stateless session beans and thesis statements issues handling all database interactions programmatically (through pooled JDBC connections). EJBs are slower and more complex than proprietary server implementations when high scalability is not needed. Java (to 1.3) does not have non-blocking I/O, which virtually guarantees Java server implementations bind one thread per client connection. This limits communication throughput. Some Java application servers provide proprietary non-blocking I/O to improve throughput. From the 1.4 SDK, Java includes non-blocking I/O. Using java.lang.reflect.Proxy (Page last updated July 2001, Added 2001-07-20, Author Tom Harpin, Publisher Sun). Tips: Interposing proxy objects is a useful approach to trace or profile method calls. Essays Critiquing Article? The java.lang.reflect.Proxy class allows you to create a wrapper around any object which implements an thesis statements for controversial interface. Appendix A (Garbage Collection) of Java Platform Performance: Strategies and Tactics. (Page last updated 2001, Added 2001-04-20, Authors Steve Wilson, Jeff Kesselman, Publisher Sun). Thesis On Child In India? Tips: Large RAM requirements can force the OS to thesis for controversial issues use virtual memory, which slows down the essay on summer vacation, application.
Most JVM implementations will not dereference temporary objects until the thesis statements for controversial issues, method has gone out of how to, scope, even if the object is created in an inner block which has gone out of scope. So you need to for controversial explicitly null the variable if you want it collectable earlier. Adding a finalizer method extends the life of the on child rights in india, object, since it cannot be collected until the finalize() method is run. Do not use finalizers to free resources in a timely manner. Various performance tips from a JavaOne 1998 presentation. (Page last updated September 1998, Added 2000-12-20, Author Tony Squier Steven Meloan, Publisher Sun). Tips: Minimize the number of times that an for controversial applet has to request data from the essays, server. Package Applet images into a single class file.
Use Thread pools where these improve performance. Use BufferedIO streams to access URLConnection's Input/Output streams. Load Balancing Web Applications (Page last updated September 2001, Added 2001-10-22, Author Vivek Veek, Publisher OnJava). Tips: DNS round-robin sends each subsequent DNS lookup request to for controversial the next entry for that server name. This provides a simple machine-level load-balancing mechanism, but is only appropriate for session independent or shared-session servers. Essays Critiquing Article? DNS round-robin has no server load measuring mechanisms, so requests can still go to overloaded servers, i.e. the load balancing can be very unbalanced. Thesis? Hardware load-balancers solve many of the problems of without, DNS round-robin, but introduce a single point of failure. A web server proxy can also provide load-balancing by redirecting requests to multiple backend webservers. Article on using CachedRowSet, a ResultSet that doesn't need continuous connection to the database (Page last updated February 2001, Added 2001-02-21, Author Taylor G. Cowan, Publisher JavaWorld).
Tips: CachedRowSet provides cached result sets that do not require continuous connection to the database, allowing connections to statements for controversial be reused more efficiently. Using CachedRowSet lets you batch updates, and execute them asynchronously. Copy? CachedRowSet also supports offline work which is statements for controversial, later synchronized. CachedRowSet is probably not appropriate for managing large datasets. JMS vs RMI (Page last updated February 2002, Added 2002-02-22, Author Kevin Jones, Publisher DevX). Essay? Tips: RMI calls marshall and demarshall parameters, adding major overhead.
Every network communication has several overheads: the distance between the sender and the receiver adds a minimum latency (limited by the speed the signal can travel along the wire, about two-thirds of the speed of light: London to New York would take about 3 milliseconds); each network router and thesis for controversial issues switch adds time to respond to data, on essays article the order of 0.1 milliseconds per device per packet. Thesis Issues? Part of most network communications consists of small control packets, adding significant overhead. One RMI call does not generally cause a noticeable delay, but even tens of RMI calls can be noticeable to rights in india the users. Beans written with many getXXX() and setXXX() methods can incur an RMI round trip for every data attribute. Thesis Statements For Controversial Issues? Messaging is naturally asynchronous, and allows an application to decouple network communications from ongoing processing, potentially avoiding threads from being blocked on communications. Proxy code generation (Page last updated February 2002, Added 2002-02-22, Author Paul McLachlan, Publisher Java Developers Journal). Tips: Generative programming is a class of techniques that allows for more flexible designs without the performance overhead often encountered when following a more traditional programming style. JSP engines are one example. java.lang.reflect.Proxy is another. Scholarship Application Without Essays? More advanced code obfuscations (such as control-flow obfuscation) can produce slower programs as the obfuscated bytecode is more difficult to optimize by thesis statements the JIT or HotSpot compiler. A reflective lookup [obtaining the method reference from its name] is much slower than a reflective invoke [invoking the method from the reference] once you have a method reference. Essays Of Christmas? [Article provides an implementation of the JNI call using the JVM_OnLoad() function to trap class bytecodes as they are loaded].
A generated Proxy class uses the Reflection API to look up the interface methods once in its static initializer, and generates wrappers and access methods to handle passing primitive data between methods. [This means that a generated Proxy class will have a certain amount of overhead compared to the equivalent coded file]. Finalizers (Page last updated March 2002, Added 2002-04-26, Author Phil Vickers, Publisher IBM). Thesis? Tips: Adding finalizers to your code makes GC much more expensive and unpredictable. Finalizers are not executed at a predictable time. Sun community chat session: Tuning the Java Runtime for Big Iron (Page last updated March 2001, Added 2001-04-20, Author Edward Ort, Publisher Sun). Tips: Use the -server option. Use -XX:+UseLWPSynchronization (better threading) or on Solaris set LD_LIBRARY_PATH=/usr/lib/lwp:/usr/lib (even better threading). Set the copy essay, young generation space to 1/4 to 1/3 of heap space, e.g. Issues? -Xms1024m -Xmx1024m -XX:NewSize=256m -XX:MaxNewSize=256m. On Solaris use vmstat, pstat (utilities) and -verbose:gc (runtime option). GC is single-threaded (at least to 1.3.x), so cannot take advantage of multiple-CPUs (i.e. can end up with multi-processor mostly idle during GC phases if using a single JVM).
Too many threads can lead to thread starvation [presumably thrashing]. Use at least one thread per essay vacation for class, CPU, more if any threads will be i/o blocked. On Solaris use the statements for controversial, mpstat utility to essays critiquing monitor CPU utlization. 1.4 will include concurrent GC that should avoid large GC pauses. The biggest performance problem is bad design. Use: -XX:NewSize=value -XX:MaxNewSize=value rather than -XX:SurvivorRatio and -XX:NewRatio. Set initial heap size to max heap size when you know what size heap you'll want and you want to avoid wasting time growing the heap as you'll fill up space. Statements Issues? If you're not sure how big you'll want your heap to be you might want to set a smaller initial size and only grow to use the space if you need it. Low CPU utilization together with bad performance may indicate GC, synchronization, I/O or network inefficiencies. -XX:MaxPermSize affects Perm Space size (storage for HotSpot internal data structures), and only needs altering if a really large number of classes are being loaded. [The session also discussed some Solaris OS parameters to tune]. For JDK 1.3, the heap is: TotalHeapSize = -Xmx setting + MaxPermSize; with -Xmx split into new and old spaces [i.e. total heap space is old space + new space + perm space, and settable heap using -Xmx defines the size of the old+new space. -XX:MaxNewSize defines how much of -Xmx heap space goes to new space].
Looks at Bluestone Total-e-server, Sybase Enterprise Application Server, SilverStream Application Server, and WebLogic Application Server. (Page last updated February 2001, Added 2001-03-21, Author Abraham Kang, Publisher JavaWorld). Tips: A cluster in this context is a group of machines working together to transparently provide enterprise services. Thesis For Controversial? A cluster can be implemented using a dispatcher which accepts requests and passes them on essay on summer vacation to other servers (either by redirecting the client or directly). Clusters target to provide scalability and thesis statements issues high-availability. J2EE application servers implement clustering around their implementation of JNDI.
Clustering should allow failover if a machine/process crashes. Thesis Rights In India? For stateful sessions, this requires state replication. Database and filesystem session persistence can limit scalability when storing large or numerous objects in the HttpSession. To scale the for controversial issues, static portions of your Website, add Web servers; to scale the essays, dynamic portions of your site, add application servers. Multicasting efficiency (Page last updated January 2002, Added 2002-02-22, Author Paul Timberlake, Publisher Message MQ).
Tips: When dealing with large numbers of active listeners, multicast publish/subscribe is more efficient than broadcast or multiple individual connections (unicast). When dealing with large numbers of listeners with only a few active, or if dealing with only statements issues, a few listeners, multicasting is inefficient. This scenario is common in enterprise application integration (EAI) systems. Inactive listeners require all missed messages to copy without be resent to for controversial issues them in order when the thesis rights in india, listener becomes active. Statements For Controversial Issues? A unicast-based message transport, such as message queuing organized into a hub-and-spoke model, is more efficient than multicast for most application integration (EAI) scenarios. NIO (Page last updated Daniel F. Savarese, Added 2002-02-22, Author February 2002, Publisher JavaPro). Tips: GatheringByteChannel lets you to write a sequence of bytes from multiple buffers, and ScatteringByteChannel allows you to read a sequence of bytes into multiple buffers. Both let you minimize the number of essays, system calls meade by combining operations that might otherwise require multiple system calls.
Selector allows you to multiplex I/O channels, reducing the number of for controversial, threads required for efficient concurrent I/O operations. FileChannels allow files to be memory mapped, rather than reading into a buffer. This can be more efficient. [But note that both operations bring the file into memory in different ways, so which is faster will be system and data dependent]. Optimizing Searches via Rare Events (Page last updated April 2002, Added 2002-05-19, Authors ANDREA MONTANARI RICCARDO ZECCHINA, Publisher Nature). Tips: Re-starting a search algorithm at random times can improve the thesis on child rights, average time required to statements for controversial reach the solution. Compression in Java (Page last updated February 2002, Added 2002-02-22, Author Qusay H. Scholarship? Mahmoud and thesis statements for controversial issues Konstantin Kladko, Publisher Sun). Tips: Compression techniques have efficiencies that vary depending on the data being compressed. It's possible a proprietary compression technique could the most efficient for a particular application. For example, instead of transmitting a compressed picture, the rights in india, component objects that describe how to draw the picture may be a much smaller amount of data to statements for controversial transfer.
ZIPOutputStream and GZIPOutputStream use internal buffer sizes of 512. BufferedOutputStream is unnecessary unless the size of the buffer is significantly larger. GZIPOutputStream has a constructor which sets the internal buffer size. Scholarship Application Without Essays? Zip entries are not cached when a file is thesis statements issues, read using ZipInputStream and FileInputStream, but using ZipFile does cache data, so creating more than one ZipFile object on the same file only opens the file once. Essay? In UNIX, all zip files opened using ZipFile are memory mapped, and therefore the performance of ZipFile is superior to ZipInputStream. If the contents of the same zip file, are frequently changed then using ZipInputStream is more optimal. Compressing data on the fly only improves performance when the thesis statements, data being compressed are more than a couple of hundred bytes. Porting to KVM (Page last updated February 2002, Added 2002-02-22, Author Shiuh-Lin Lee, Publisher Micro Java). Tips: Minimize program runtime size. Avoid third-party class libraries if not necessary, for example kAWT (a GUI toolkit library) and essay on summer vacation MathFP (Fixed point math).
Store big lookup tables in the user database rather than as part of the statements issues, program. Call GC functions manually. Dispose of Objects; close the database and the network connections as soon as they are no longer needed. Only load or transfer minimal required data structures and records into memory. Avoid float and double calculations. Avoid data conversions: store and essays use the data in the final required format, or execute conversions on the server. Statements For Controversial Issues? Use client caching. Data compression has to essays be tuned to minimize both client CPU impact as well as transfer size. Thesis Statements For Controversial Issues? Use tabbed panels to hold different groups of information. Essays? Scrollable panel can have higher memory requirements than a tabbed panel. Avoid some KVM user components (like ScrollTextBox), because they are runtime memory hogs.
Use selection lists rather than manual entry to speed up user data entry. Tracking Memory leaks (Page last updated February 2001, Added 2001-03-21, Author Jim Patrick, Publisher IBM). Tips: An object is only counted as being unused when it is no longer referenced. If objects remain referenced unintentionally, this is statements issues, a memory leak. Critiquing Article? If you get a java.lang.OutOfMemoryError after a while, memory leakage is a strong suspect. If an for controversial issues application is meant to run 24 hours a day, then memory leaks become highly significant.
Most JVMs grow towards the upper heap limit (-Xmx/-mx options) when more memory is required, and do not return memory to essays of christmas the operating system, even if the memory is no longer needed, until the thesis statements for controversial, JVM process terminates. [Article provides an how to write example of tracking memory leaks using JProbe]. BigDecimal and thesis statements Enumerations (Page last updated August 2001, Added 2001-08-20, Author Glen McCluskey, Publisher Sun). Tips: BigDecimal provides arbitrary-precision floating point number arithmetic, at the cost of performance. Type-safe enumeration is safer than using ints for enum values, and you can still use comparison by identity for fast performance. But you lose the performance potential of using the enum values directly as array indices, switch constants and bitmasks. Article on connection pools (Page last updated September 1999, Added 2001-02-21, Author Hans Bergsten, Publisher Web Developers Journal). Unit? Tips: Reuse database connections using a connection pool.
Put helper classes (non-servlet classes used by thesis statements for controversial servlets) in thesis on child rights in india the CLASSPATH of the servlet engine. Weblogic's RMI framework (Page last updated January 1999, Added 2001-03-21, Author , Publisher BEA). Tips: Use a single, multiplexed, asynchronous, bidirectional connection for RMI client-to-network traffic instead of the standard reference implementation using multiple sockets. Try to statements for controversial improve the serialization mechanism for faster RMI [Externalization is better]. Use local calls for objects located in the same JVM. Minimize distributed garbage collection. Use smart stubs which provide data caching and localized execution in addition to the normal remote execution and application data fetching capabilities. Using VolatileImage (Page last updated May 2001, Added 2001-07-20, Author [email protected], Publisher Sun). Tips: Graphics performance in 1.2 is worse than 1.1. 1.3 is better, and 1.4 should be the fastest yet.
From 1.2 direct access to image pixels was available, but was too slow to be usable because it involved copying many bits around in memory. Use BufferedImage to issues move offscreen images to system memory rather than copying pixels. For even faster image mapping, VolatileImage allows a hardware-accelerated offscreen image to be drawn directly on the video card. VolatileImage is of christmas, volatile because the image can be lost at any time, from various causes: running another application in fullscreen mode; starting a screen saver; changing screen resolution; interrupting a task. Only constantly re-rendered images need to be explicitly created as VolatileImage objects to be hardware accelerated. Statements For Controversial Issues? Such images include backbuffers (double buffering) and animated images. All other images, such as sprites, can be created with createImage, and Java 2D will attempt to critiquing accelerate them. If an image, such as a sprite, is drawn once and copied from thesis issues many times, Java 2D makes a copy of it in essays accelerated memory and future copies from the image can perform better. Thesis For Controversial Issues? To render sprites to rights in india the screen, you should use double-buffering by: creating a backbuffer with createVolatileImage, copying the sprite to the backbuffer, and copying the backbuffer to the screen. If content loss occurs, Java 2D re-copies the sprite from thesis for controversial issues software memory to accelerated memory.
Only some graphics operations (e.g. curved shapes) are accelerated on unit some platforms. Use profiling to determine what works best for your situation. Thesis For Controversial? From 1.4 Swing uses VolatileImage for its double buffering. VolatileImage.getCapabilities() provides an ImageCapabilities object which gives details of the details of the essay without, runtime VolatileImage. Thesis For Controversial? The ImageCapabilities allows the application to essay without decide to use less images, images of lower resolution, different rendering algorithms, or various other means to attempt to get better performance from the current situation and platform.
Sun community chat session on Optimizing Java Program Performance with Peter Haggar. (Page last updated January 2001, Added 2001-02-21, Author Edward Ort, Publisher Sun). Thesis For Controversial Issues? Tips: Try faster JVMs if possible. Never tune code unless you have identified a performance problem with a profiling tool. Beware that tuning techniques may not work well on all platforms. Speed start-up time by: minimizing the .class sizes (use -g:none or a shrink tool e.g. DashO, JAX, JOpt); turn off the JIT Good design, data structures, and application without algorithms are the best things to produce good performance. Check String manipulation code. Thesis Statements For Controversial Issues? It is much more efficient to read data from essay on summer 7 disk all at once rather than with multiple reads. Use the buffered classes when doing i/o. import is a compile time function, so has no effect on runtime (i.e. import a.b.*; or import a.b.c; make no difference to runtime performance). Optimize conditionals to thesis statements for controversial have the most likely true results first. Java transaction management (JTS) (Page last updated April 2002, Added 2002-04-26, Author Brian Goetz, Publisher IBM).
Tips: A container managing transactions can identify communications to the same database, and automatically convert a two-phase transaction into a more efficient single-phase commit. Article about frameworks and the effective memory management of essays, objects; avoiding memory leaks by design. (Page last updated January 2001, Added 2001-01-19, Author Leonard Slipp, Publisher Java Report). Tips: Define the life cycles of thesis statements issues, objects and of christmas the duration of object interrelationships. Then manage objects according to whether the framework retains exclusive control of them, or whether the object can be accessed from outside the framework. Minimize the number of objects that can be accessed from thesis statements issues outside the framework. Critiquing Article? In general, the creator of an statements for controversial object should be responsible for the objects' life cycle. Where this is not the case, the transfer of essay, ownership of the object should be explicit and emphasized. Similarly object relationship management should be explicit and reversible: for every add() action, there must be a remove(); for every register() action, there must be a deregister(). Various strategies for for controversial, connecting to databases (Page last updated March 2001, Added 2001-04-20, Author Prakash Malani, Publisher Java Report). Tips: Use pooled connections to essays reduce connection churn overheads. javax.sql.DataSource provides a standard connection pooling mechanism [example included]. Thesis For Controversial Issues? Obtain and release pooled conections within each method that requires the resource if the connection is very short (termed Quick Catch-and-Release Strategy in the article).
However do not release the connection only to use it again almost immediately, instead hold the connection until it will not be immediately needed. The performance penalty of obtaining and releasing connections too frequently is quite small in comparison to potential scalability problems or issues raised because EntityBeans are holding on to the connections for too long. The Quick Catch-and-Release Strategy is the best default strategy to ensure good performance and on child scalability. Basic article on performance tuning techniques. (Page last updated January 2001, Added 2000-12-14, Author Tarak Modi, Publisher Java Pro). Tips: [The compiler concatenates strings where they are fully resolvable, so don't move these concatenations to runtime with StringBuffer.] Where the compiler cannot resolve concatenated strings at compile time, the code should be converted to StringBuffer appends, and the StringBuffer should be appropriately sized rather than using the default size. For Controversial? Using the concatenation operator (+) in a loop is very inefficient, as it creates many intermediate temporary objects. Presizing collections (like Vector) to the expected size is more efficient than using the default size and letting the collection grow. Removing elements from a Vector will necessitate copying within the Vector if the element is removed from anywhere other than the end of the collection.
Cache the size of the collection in a local variable to use in a loop instead of repeatedly calling collection.size(). Unsynchronized methods are faster than synchronized ones. [Article discusses applying these optimzations to a thread pool implementation.] Object creation tuning (Page last updated 2000, Added 2001-07-20, Author Daniel F. Savarese, Publisher Numega). Tips: Creating and dereferencing too many objects can adversely impact performance. Essays Of Christmas? Avoid holding on to objects for too long by explicit dereference (setting variables to thesis null) and by using weak references. Use a profiler to determine which objects may be created too often, or may not be being dereferenced. Essays Of Christmas? When looking for memory problems, look at statements for controversial methods that are called the most times or use the most memory.
Frequently called methods may unnecessarily allocate objects on each call. Methods that use a lot of on summer for class 7, memory may not need to use as much memory or they may be a source of thesis statements, memory leaks. Essays? Try to use mutable objects like StringBuffers or a char array instead of immutable objects like String. Don't restrict object state initialization to the arguments passed to a constructor. Provide a zero-argument constructor that creates reasonable default values and include setter methods or an init method to allow objects of statements for controversial issues, that class to be reused. If you have to write unit wrap primitive types, such as an thesis for controversial issues int, define your own wrapper class which can be reused instead of using java.lang.Integer. If you need to create many instances of a wrapper class like Integer, consider writing your algorithm to of christmas accept primitive types. Use a factory class instead of directly calling the new operator, to allow easier reuse of objects. Object pooling and database connection pooling are two techniques for statements for controversial issues, reducing object creation overheads. Object pools can be sources or memory leaks and can themselves be inefficient. The java.nio packages (updated) (Page last updated December, 2001, Added 2001-10-22, Author John Zukowski, Publisher Sun).
Tips: Direct buffers have a higher creation cost than non-direct buffers because they use native system operations rather than JVM operations. Direct buffers optimize access operations by using the essays of christmas, system's native I/O operations. Reduce threads by statements issues multiplexing I/O using selectors: The new I/O capabilities, allow you to create a Web server that does not require one thread per connection. How to Climb a B-tree (Page last updated December 2001, Added 2001-12-26, Author Rick Grehan, Publisher JavaPro). Tips: A B-tree outperforms a binary tree when used for external sorting (for example, when the index is stored out on of christmas disk) because searching a binary tree cuts the issues, number of keys that need searching in application without half for every node searched, whereas B-tree searching cuts the number of keys that have to be searched by approximately 1/n, where n is the number of thesis statements issues, keys on a node. B-tree variants provide faster searching at the cost of scholarship application without essays, slower insertions and deletions. Two such variants are the B-tree with rotation (more densely packed nodes) and the B+tree (optimized for sequential key traversing). [Article discusses building a B-tree class, and issues persisting it to provide a disk-based searchable index].
Database comparison (Page last updated February 2002, Added 2002-04-26, Author Timothy Dyck, Publisher E-Week). Tips: SQLServer has driver problems that slow access to it. Connection memory requirements vary dramatically between databases, and affect how much memory can be allocated to other resources. In-memory query result caches (such as with mySQL) improves performance significantly. (Works by retrieving cached results of byte-for-byte identical queries, with no query compilation required). Add extra indexes. Arrange the stored order of application without essays, rows to best satisfy the queries. Some drivers store the entire result set in memory when using bidirectional cursors - which does not scale. File Channels, StackTraceElements, (Page last updated May 2002, Added 2002-05-19, Author Glen McCluskey, Publisher Sun). Statements For Controversial Issues? Tips: File Channels (from the 1.4+ nio package) provide optimized mapping and a transferTo() method which is the fastest way to copy files. StackTraceElement provides access to scholarship essays the stack from thesis statements excception objects, useful for analyzing stack elements.
Article about garbage collection and finalization. (Page last updated December 2001, Added 2001-12-26, Author Jeff Friesen, Publisher JavaWorld). Tips: [No specific performance tips, but its always helpful to essay for class 7 know about GC]. Java Transaction Service (Page last updated March 2002, Added 2002-03-25, Author Brian Goetz, Publisher IBM). Tips: Writing every data block to disk when any part of it changes would be bad for system performance. Deferring disk writes to a more opportune time can greatly improve application throughput.
Transactional systems achieve durability with acceptable performance by summarizing the results of multiple transactions in a single transaction log. Thesis Statements For Controversial? The transaction log is essay on summer 7, stored as a sequential disk file and will generally only be written to, not read from, except in the case of rollback or recovery. Writing an update record to a transaction log requires less total data to for controversial issues be written to disk (only the data that has changed needs to be written) and fewer disk seeks. Changes associated with multiple concurrent transactions can be combined into a single write to the transaction log, so multiple transactions per disk write can be processed, instead of requiring several disk writes per transaction. HTTP sessions vs. Write? stateful EJB (Page last updated July 2002, Added 2002-07-24, Author Peter Zadrozny, Publisher Weblogic Developers Journal). Tips: The comparative costs of storing data in an HTTP session object are roughly the same as storing the same data in a stateful session bean. Failure to remove an EJB that should have been removed (from the HTTP session) carries a very high performance price: the EJB will be passivated which is a very expensive operation. Chapter 1, What Is Performance? of Java Platform Performance. Thesis For Controversial Issues? (Page last updated 2000, Added 2001-11-27, Author Steve Wilson and Jeff Kesselman, Publisher Sun). How To Unit? Tips: Design your software with the thesis statements issues, target configuration (e.g. RAM) in mind. If your program consumes all of your user's memory resources, they probably won't be happy.
Measure performance under loads comparable to expected deployed loads. Perceived performance is scholarship application without essays, a highly important aspect of performance. Thesis Statements For Controversial? How fast a program feels is more important than how fast it really is. Chapter 2, The Performance Process of Java Platform Performance. (Page last updated 2000, Added 2001-11-27, Author Steve Wilson and Jeff Kesselman, Publisher Sun). Tips: It's nearly impossible to achieve good performance through optimizations alone, without considering performance in analysis and design stages. Creating clear system and performance requirements is the key to evaluating the success of your project.
Use cases provide excellent specifications for building benchmarks. Specify the essays critiquing article, limitations of the application: well-defined boundaries on the application scope can provide big optimization opportunities. Specifications should include system and performance requirements, including all supported hardware configurations (RAM/CPU/Disk/Network) and other software that normally executes concurrently. You should specify quantifiable performance requirements, for example a response time of two seconds or less. Thesis Statements For Controversial? Scalability is more dependent on essays good design decisions than optimal coding techniques. Encapsulation leads to slowdowns from increased levels of indirection, but is essential in large, scalable, high-performance systems. For example, using a java.util.List object may be slower than using a raw array, but allows you to change very easily from ArrayList to LinkedList when that is faster. Meeting or exceeding your performance requirements should be part of the shipping criteria for your product.
Once you've determined that a performance problem exists, you need to thesis statements issues begin profiling. Profilers are most useful for identifying computational performance and RAM footprint issues. Performance tuning is an copy iterative process. Data gathered during profiling needs to be fed back into the development process. Chapter 3, Measurement Is Everything of Java Platform Performance. (Page last updated 2000, Added 2001-11-27, Author Steve Wilson and Jeff Kesselman, Publisher Sun). Thesis Issues? Tips: Benchmarks are typically time-related, but can also measure quantities such as how much memory is used. A stopwatch is write unit, a versatile benchmarking tool. Statements For Controversial Issues? System.currentTimeMillis() provides millisecond timing for unit, benchmarking [A Stopwatch class based on thesis statements issues using System.currentTimeMillis() is presented]. Use benchmarks to: Compare the performance of alternative solutions; Profile performance; Track performance changes. Micro-benchmarks (repeatable sections of essay vacation, code) can be useful but may not represent real-world behavior.
Factors that can skew micro-benchmark performance include Java virtual machine warm-up time, and global code interactions. Macro-benchmarks (repeatable test sequences from the user point of view) test your system as actual end users will see it. Extract minima, maxima and averages from repeated benchmark data for analysis. Use these to thesis issues compare progress of benchmarks during tuning. [I like to scholarship application add the 90th-centile value too]. Profilers help you find bottlenecks in applications, and should show: the methods called most often; the methods using the largest percentage of time; the methods calling the most-used methods; and the methods allocating a lot of memory. The Sun JVM comes with the hprof profiler. Bottlenecks can be tuned by making often-used methods faster; and by calling slow methods less often.
Backtrace methods to understand the context of the bottleneck. For example, caching a value may be a better optimization than speeding up the repeated calculation of that value. Memory usage is often of issues, critical importance to the overall application performance. Excessive memory allocation is essay, often one of the first things that an experienced developer looks for when tuning a Java program. Examine bottlenecks for memory allocation. For example you may be able to replace a repeated object allocation in a loop with a reusable object allocated once outside the thesis statements, loop.
Memory leaks (not releasing objects for the garbage collector to reclaim) can lead to a large memory footprint. Application? You identify memory leaks by: determining that there is a leak; then identifying the objects that are not being garbage colleted; then tracing the references to those leaking objects to determine what is holding them in memory. Thesis Issues? If your program continues to use more and how to write unit more memory then it has a memory leak. Thesis Statements Issues? This determination should happen after all initializations have completed. Identify memory leak objects by marking/listing the objects in essay vacation for class 7 some known state, then cycling through other states and statements for controversial back to 7 that known state and seeing which extra objects are now present. When there are obvious bottlenecks, the method profile should show these. A flat method profile is one where there are no obvious bottlenecks, no methods taking vastly more time than others. In this case you should look at cumulative method profiles, which show the thesis for controversial issues, relative times taken by a method and all the vacation, methods it calls (the call tree ). This should identify methods which are worthwhile targets for optimization. Chapter 4, I/O Performance of Java Platform Performance: Strategies and statements for controversial Tactics. (Page last updated 2000, Added 2001-12-27, Author Steve Wilson and Jeff Kesselman, Publisher Sun).
Tips: Buffer i/o operations. Custom buffering (using your own array of bytes/chars) is essays, quicker than using a Buffered class. Application specific i/o can be tuned, e.g. Statements? caching in memory frequently served pages of a HTTP server. Rights? Default Serialization is slow. Use the transient keyword to define fields to thesis issues avoid having those fields serialized. Examine serialized objects to essay without determine which fields do not need to be serialized for the application to work. Chapter 5, RAM Footprint of Java Platform Performance: Strategies and Tactics. (Page last updated 2000, Added 2001-12-27, Author Steve Wilson and Jeff Kesselman, Publisher Sun). Thesis Statements Issues? Tips: Virtual memory is write unit, many times slower than RAM: try to fit the application into available RAM on the target platform.
Runtime.totalMemory() and Runtime.freeMemory() measure available heap memory, but not the RAM footprint of the application. Use operating system monitoring tools to determine the RAM footprint of the application: e.g. Statements For Controversial? task manager on in india Windows NT, pmap -x and ps on Solaris. Small GUI apps need several hundred classes to issues be loaded just to start the app. Small GUI apps need to reduce the rights in india, number of classes loaded to improve startup time. For Controversial Issues? You can approximate sizes of vacation 7, objects based on the number of fields and their types: byte-1 byte; char-2 bytes; short-2 bytes; int-4 bytes; float-4 bytes; long-8 bytes; double-8 bytes; references-4 bytes. JVMs will impose additional overheads. You can determine actual object sizes for a particular JVM by measuring the heap space taken by thesis statements issues multiple instances of a class. Critiquing? Use profiling to determine the overal size cost of a class of objects, to determine whether it is worth reducing the size cost of the statements, class.
Some JVM/OS combinations can impose a significant memory overhead on each thread. Use 'java -verbose MyMainClass' to identify all classes that are loaded. Chapter 6, Controlling Class Loading of Java Platform Performance: Strategies and Tactics. (Page last updated 2000, Added 2001-12-27, Author Steve Wilson and Jeff Kesselman, Publisher Sun). Tips: To avoid loading unnecessary classes (e.g. Essay? when the JIT compiles methods which refer to unused classes), use Class.forName() instead of directly naming the class in source. This tactic is statements issues, useful if large classes or a large number of on summer 7, classes are being loaded when you don't think they need to be. Combine listener functionality into for controversial one class to avoid an explosion of critiquing article, generated inner classes. This technique increases maintenance costs.
Use a Generic ActionListener which maps instances to method calls to avoid any extra listener classes. This has the drawback of losing compile-time checks. java.lang.reflect.Proxy objects can be used to thesis statements generalize this technique to 7 multiple interfaces. Statements? Run multiple applications in the same JVM. [Chapter discusses how to do this, but see Multiprocess JVMs and Echidna for more comprehensive solutions]. Chapter 7, Object Mutability: Strings and other things of Java Platform Performance: Strategies and Tactics. (Page last updated 2000, Added 2002-02-22, Author Steve Wilson and Jeff Kesselman, Publisher Sun). Tips: The allocation, initialization, and collection of many short-lived useless objects can cause major inefficiencies in your software, even when running on an advanced runtime such as the how to, HotSpot VM. Be cautious when the number of objects you're allocating becomes very high-for example, when allocating objects inside loops.
For heavy-duty text processing, however, some uses of the String class can become major performance bottlenecks. StringBuffer can be used to improve the performance of common text processing operations. Thesis Statements For Controversial Issues? Avoid creating new strings in compute intensive parts of code. Be careful of the concatenation operators '+' and '+=' when used with strings. To avoid spurious object creation, create methods which return primitive data for multiple data items, rather than one method returning an object holding multiple data items.
Use immutable objects to prevent the need to copy objects to pass information between methods. Application Essays? Object pooling small objects is often counterproductive. Statements? The overhead of vacation, managing the object pool is often greater than the small object penalty. Pooling can also increase a program's memory footprint. Pooling large objects (e.g. large bitmaps or arrays) or objects that work with native resources (e.g. Threads or Graphics) can be efficient.
Chapter 8, Algorithms and data structures of thesis statements, Java Platform Performance: Strategies and essays of christmas Tactics. (Page last updated 2000, Added 2002-02-22, Author Steve Wilson and Jeff Kesselman, Publisher Sun). Thesis Statements Issues? Tips: Choosing the best algorithm or data structure for a particular task is one of the keys to writing high-performance software. The optimal algorithm for a task is highly dependent on the data and data size. Special-purpose algorithms usually run faster than general-purpose algorithms. Testing for easy-to-solve subcases, and unit using a faster algorithm for those cases, is a mainstay of statements for controversial issues, high-performance programming. Collection features such as ordering and duplicate elimination have a performance cost, so you should select the collection type with the fewest features that still meets your needs.
Most of the time ArrayList is the best List choice, but for some tasks LinkedList is more efficient. HashSet is much faster than TreeSet. Choosing a capacity for HashSet that's too high can waste space as well as time. Thesis On Child In India? Set the thesis statements issues, initial capacity to about twice the copy essay without, size that you expect the Set to grow to. The default hash load factor (.75) offers a good trade-off between time and space costs. Statements For Controversial Issues? Higher values decrease the space overhead, but increase the time it takes to how to write look up an entry. (When the number of thesis issues, entries exceeds the product of the scholarship without essays, load factor and the current capacity, the capacity is doubled). Programs pay the costs associated with thread synchronization even when they're used in a single-threaded environment. The Collections.sort() method uses a merge sort that provides good performance across a wide variety of situations. When dealing with collections of primitives, the overhead of allocating a wrapper for each primitive and then extracting the primitive value from the for controversial issues, wrapper each time it's used is quite high.
In performance-critical situations, a better solution is to work with plain array structures when you're dealing with collections of primitive types. Random number generation can take time. Scholarship Application? If possible you can pre-generate the random number sequence into thesis statements an array, and in india use the elements when required. Chapter 10 (Swing models and renderers) of thesis statements for controversial, Java Platform Performance: Strategies and critiquing Tactics. (Page last updated 2000, Added 2000-10-23, Authors Steve Wilson, Jeff Kesselman, Publisher Sun). Tips: Swing?s model-view architecture is critical for statements for controversial, building scalable programs. When changing data stored in models, perform the operations in write bulk whenever possible. E.g. For Controversial? use the interface that adds an array of essays, elements rather than one element at a time. Use custom models to handle large datasets.
The default models provided with Swing are generic and designed for light-duty use [i.e. Statements For Controversial? are slow]. Critiquing Article? Custom renderers can sometimes be used to improve performance. But watch out as it is easy to badly construct a custom renderer, making performance worse. Thesis? A custom model and a custom renderer can be used together in the same Component. When initializing or totally replacing the contents of a model, consider constructing a new one instead of article, reusing the existing one, as this avoid posting notifications to thesis statements for controversial any listeners. [Or reuse the thesis rights, object but deregister the listeners first]. Improving socket transfer rates (Page last updated May 2001, Added 2001-05-21, Author Rama Roberts, Publisher Sun). Tips: The usual StringBuffer better than String tip applies to socket communications too. Thesis Statements Issues? PrintWriters are not suitable for socket communications because they flush at each newline. Socket.setTcpNoDelay(true) may help speed if you have many small packets sent frequently across the connection. Server performance testing (Page last updated 2000, Added 2001-05-21, Author Floyd Marinescu, Publisher The Server Side). Tips: Test response times against average current data/user volumes, then repeat the same test against four times as much volume as you expect in for class 7 3 years time.
This defines your long term target - getting the response times the same for thesis statements issues, that latter test. Without? Response time increasing too much when database is over populated probably indicates lack of or inappropriate indexing on the database. Thesis Issues? Response time increasing exponentially as load increases, you need to improve scalability by optimizing the application or adding resources. Without? Use SQL clause with EXPLAIN or similar (e.g. Explain select * from table where tablefield = somevalue) to statements for controversial issues ensure that the database is doing an indexed search rather than a linear searches of large datasets. Use a profiler to determine object usage, garbage collection behaviour and method bottlenecks in application without essays the application. Minimize network calls, especially database calls: make one large database call rather than many small ones; make sure ejbStore isn?t storing anything for read only thesis for controversial issues, operations; use Details Objects to get entity bean state rather than making many trips for each aspect of state. Use caching where possible. Use session beans as a fa?ade to your entity beans to encapsulate the workflow of one entire usecase in essays one network call to statements for controversial issues one method on a session bean (and one transaction). Optimizing entity beans (Page last updated May 2001, Added 2001-05-21, Author Akara Sucharitakul, Publisher Sun). Tips: Use container-managed persistence when you can.
An efficient container can avoid database writes when no state has changed, and reduce reads by retrieving records at the same time as find() is of christmas, called. Minimize database access in ejbStores. Statements? Use a dirty flag to avoid writing tee bean unless it has been changed. Always cache references obtained from lookups and find calls. Always define these references as instance variables and look them up in scholarship essays the setEntityContext (method setSessionContext for session beans). Always prepare your SQL statements. Close all database access/update statements properly. Avoid deadlocks.
Note that the sequence of ejbStore calls is not defined, so the for controversial, developer has no control over the access/locking sequence to database records. EJB best practices (Page last updated April 2001, Added 2001-05-21, Author Sandra L. Emerson, Michael Girdley, Rob Woollen, Publisher Java Developers Journal). How To Write Unit? Tips: To avoid resources being held unnecessarily for long periods, a transaction should never encompass user input or user think time. Container managed transactions are preferred for consistency, and should provide extra optimization options. Don't model a shared cache or any shared resource as a stateful session bean. For Controversial Issues? Stateless session beans are easier to scale than stateful session beans. With stateful session beans, every client will need its own session bean instance, reducing scalability. Always call remove after finishing with a stateful session bean instance, otherwise the EJB container will eventually passivate the article, bean, incurring extra unnecessary disk writes. J2EE clustering (Page last updated August 2001, Added 2001-08-20, Author Abraham Kang, Publisher JavaWorld). Tips: Consider cluster-related and load balancing programming issues from the beginning of the thesis, development process. Load balancing has two non-application options: DNS (Domain Name Service) round robin or hardware load balancers. [Article discusses the pros and cons].
To support distributed sessions, make sure: all session referenced objects are serializable; store session state changes in a central repository. Essays? Try to keep multiple copies of objects to a minimum. SoftReference-based HashMap (Page last updated August 2001, Added 2001-08-20, Author Heinz Kabutz, Publisher Kabutz). Tips: WeakHashMaps are not ideal if you want the values to be weakly referenced rather than the keys. SoftReferences may be better for memory sensitive caches since they are supposed to be collected in the reverse order to which they were last referenced. Thesis Statements? Adding the application, capability to strongly reference some of the values ensures those objects will be retained through a garbage collection. Avoiding memory leaks in EJBs (Page last updated April 2001, Added 2001-05-21, Author Govind Seshadri, Publisher IT World). Tips: Make sure that any beans which have session scope implement the HttpSessionBindingListener interface Explicitly release any resources that may be used within the statements for controversial issues, bean by implementing the essays, valueUnbound() callback. Explicitly release the statements issues, user's session by invoking invalidate() when they log out.
Try setting the session invalidation interval to a smaller value than the essay vacation 7, default 30 minutes. Make sure that you are not placing any large grained objects into the servlet context (application scope) as that can also prove problematic sometimes. Parallel clustering of issues, machines using Java (Page last updated April 2001, Added 2001-04-20, Author Aashish N. Patil, Publisher IBM). Essays Critiquing Article? Tips: [Article describes an implemented architecture for distributing Runnable threads across multiple computer nodes]. The Javap disassembler (Page last updated August 2000, Added 2001-04-20, Author Stuart Halloway, Publisher Sun). Tips: [Article describes using the javap disassembler, useful for statements, identifying exactly what the code has been compiled into]. Use the javap disassembler to determine the how to write unit, efficiency of generated bytecodes. javap is not sufficient to determine code efficiency, because JIT compilers can apply additional optimizations. Speeding up file searching in JFileChooser (Page last updated February 2001, Added 2001-03-21, Author Slav Boleslawski, Publisher JavaWorld).
Tips: [Article discusses JFileChooser's operation in thesis statements issues detail, including multi-threading, filename caching and batched delivery. Article discusses how to how to unit add type-ahead lookup functionality to choosing files]. Various tips. (Page last updated 1999?, Added 2000-10-23, Author Nate Sammons, Publisher Sammons). Thesis Issues? Tips: Use StringBuffer for String concatenations, rather than the '+' operator. Use static strings, String.intern() or a static Hashtable to reduce the number of essays of christmas, occurrances of identical string objects. Modify java.lang.String to statements for controversial cache the hashCode if you are using many string keys in hash tables [note Sun added this optimization to the String class in how to SDK 1.3] String.getBytes() is very inefficient with a method call for every character.
Use getBytes(int, int, byte int) instead, or some other mecahnism. Use non-synchronized Vector, Hashtable, etc. where possible. Thesis Statements? Size Vector, Hashtable, etc. appropriately. Object creation is expensive. Pool your objects where possible. Inner class object creation is write unit, even more expensive than normal. Use non-public concrete support classes instead. Method call times: static 220ns; final 300ns; instance 550ns; interface methods 750ns; synchronized methods 1,500ns. [But times vary enormously depending on the VM and context]. Use static final methods where possible. [And do functional programming too ;-)] Rewrite loops so that the termination test compares against 0. Statements For Controversial? Use exception terminated infinite loops for copy without, long loops. Use System.arraycopy() to copy arrays. Use temporary local variables to manipulate instance variables.
EJB2 clustering with application servers (Page last updated December 2000, Added 2001-01-19, Author Tyler Jewell, Publisher OnJava). Tips: [Article discusses multiple independent ways to load balance EJBs] Sun community chat session with Steve Wilson and Jeff Kesselman on issues Java Performance (Page last updated August 2000, Added 2001-01-19, Author Edward Ort, Publisher Sun). Tips: HotSpot JVMs can return heap memory to the OS while running. Essay Vacation? HotSpot Client VM (JVM 1.3) is optimized for quick startup time and low-memory footprint. The server VM (HotSpot 1.0/2.0) is designed for peak performance (may take a little longer to get up-to-speed but it will go faster in the end). Always use System.arraycopy to copy arrays.
Sticky applets available with the 1.3 plugin speeds startup (persistently caches classes on clients). Also put resources together into jar file to reduce download requests. SwingSet2 (demo in SDK distribution) provides a good example of large numbers of Swing components in a window, created asynchronously. Don't use use finalizers for anything that must be done in a timely manner. Use primitives and thesis statements for controversial issues transients to speed up serialization. Use a concentrator object to essays limit the repaint events to once every 100 milliseconds in heavily loaded systems and in multi-threaded swing environments. There is some overhead for context switching (using invokeLater) into the AWT-event thread, which you want to statements issues minimize. The key to high performance code is organization and process.
Write clean, well encapsulated code, then use a Profiler to find your true bottlenecks and tune those. Experiences building a servlet (Page last updated June 2001, Added 2001-06-18, Author Asif Habibullah, Jimmy Xu, Publisher Java Pro). Tips: Keep the thesis on child, size of the client tier small so that downloads are fast. Use the servlet init() and for controversial issues destroy() methods to start and stop limited and expensive resources, such as database connections. Make the servlets thread-safe and use connection pooling. Use PreparedStatements rather than plain Statement objects. Essay Vacation? Use database stored procedures.
Typesafe Enumeration gotchas (Page last updated January 2002, Added 2002-01-25, Author Vladimir Roubtsov, Publisher JavaWorld). Tips: Implement readResolve() for Serializable Enumeration classes to maintain object identity. Ensure that the for controversial issues, same Classloader always loads the Enumeration class to how to unit maintain object identity. Reference objects (Page last updated January 2002, Added 2002-01-25, Author Jeff Friesen, Publisher JavaWorld). Tips: Cache objects such as images in memory for quicker presentation after the first display request. Use Reference objects to hold cached objects so that the garbage collector can free space when required. [Article discusses in detail the various Reference object types]. Optimizing Java for intensive numeric calculations (Page last updated January 2002, Added 2002-02-22, Author James W. Cooper, Publisher DevX). Tips: Allocating on thesis statements issues the heap (as with object creation) is much slower than allocating on the stack.
Making numbers into article first-class objects imposes a significant overhead on calculations. Hand applied optimizations may be superceded by future compiler optimizations. Use specialized subtypes to statements reduce dynamic dispatching. Replace objects with their data held and thesis on child rights passed as local variables. OS Signal handling in Java (Page last updated January 2002, Added 2002-02-22, Author Chris White, Publisher IBM). Tips: [Article describes how to handle operating system signals from thesis statements issues within Java. Thesis On Child Rights In India? Useful if you want your application to be able to thesis for controversial respond to the full gamut of system and user actions].
Natively compiled code from Java source (Page last updated January 2002, Added 2002-02-22, Author Martyn Honeyford, Publisher IBM). Tips: Natively compiled code generated from essay without Java source might be faster and might require less memory and disk resources. [But this articles show some JVMs can be faster]. When you include the disk size of the JVM libraries, a natively compiled Java application is significantly smaller in disk size. When considering compiling Java applications to native code determine exactly what problem (or problems) you are hoping to solve with native compilation, and try all the available native compilers. RMI arguments (Page last updated December 2001, Added 2002-02-22, Author Scott Oaks, Publisher Java Report). For Controversial Issues? Tips: Some application servers can automatically pass parameters by reference if the article, communicating EJBs are in the same JVM.
To ensure that this does not break the thesis statements, application, write EJB methods so that they don't modify the parameters passed to thesis them. Choosing an application server (Page last updated January 2002, Added 2002-02-22, Author Sue Spielman, Publisher JavaPro). Tips: A large-scale server with lots of thesis for controversial issues, traffic should make performance its top priority. Performance factors to essays consider include: connection pooling; types of JDBC drivers; caching features, and their configurability; CMP support. Inability to scale with reliable performance means lost customers. Scaling features to consider include failover support, clustering capabilities, and load balancing. Notated keys to thesis statements for controversial issues access elements of nested Maps. On Child In India? (Page last updated January 2002, Added 2002-02-22, Author Matt Liotta, Publisher DevX). Tips: Use dot separated, concatenated strings to thesis statements for controversial issues optimize access to on child in india elements of nested Maps by thesis for controversial caching elements in unit the top level Map. The Garbage Collector (Page last updated January 2002, Added 2002-01-25, Author Phil Vickers, Publisher IBM).
Tips: In most current JVMs (prior to 1.4) GC starts off by locking out thesis statements issues, all other threads in the JVM. GC is a stop-the-world, synchronous operation. Non-generationl GC requires scanning the stacks of every thread and the entire Java heap. Without? Calling System.gc() explicitly is thesis statements for controversial issues, not good for performance, as it can be called when GC is not necessary, but will still result in a long pause of all JVM operations. Object management (Page last updated January 2002, Added 2002-01-25, Author Mark Bluemel, Publisher IBM). Tips: Avoid retaining objects accidentally, by holding references beyond an appropriate time for their release.
Use profiling tools to identify unintentionally retained objects. Essays Of Christmas? Garbage collection is not free; other processing will be paused during GC. Try to thesis statements issues reuse objects in preference to discarding and application without essays re-creating them. JViewport scrolling performance (Page last updated January 2002, Added 2002-01-25, Author Heather Brailsford, Publisher IBM). Tips: JViewport.BLIT_SCROLL_MODE is the default scrolling mode for JViewport in SDK 1.3 (available since 1.2.2). This mode paints directly to the screen instead of thesis statements issues, being buffered offscreen. Essays Of Christmas? This normally provides optimal performance and thesis for controversial issues minimum memory requirements. However complex images may display some intermediate paint operations if the scholarship application without essays, painting is not fast enough, giving jerky or flashing images. If this is unacceptable, try the alternate modes: setScrollMode(BACKINGSTORE_SCROLL_MODE) (intermediate performance, higher memory requirements); or setScrollMode(JViewport.SIMPLE_SCROLL_MODE) (slowest). Using JNI Get* calls (Page last updated January 2002, Added 2002-01-25, Author Mark Bluemel, Publisher IBM).
Tips: If you use JNI Get* calls (for example, GetStringCritical), you must always use the corresponding Release* call (for example, ReleaseStringCritical) when you have finished with the data, even if the isCopy parameter indicates that no copy was taken. Servlet 2.3 events (Page last updated January 2002, Added 2002-01-25, Author Budi Kurniawan, Publisher DevX). Tips: The Servlet 2.3 specification adds application and session events. [Event driven applications can often be scaled more easily than process driven applications]. Sun presentation on J2SE performance strategies (originally accessed from Reginald Hutcherson's page) (Page last updated May 2001, Added 2001-06-18, Author Reginald Hutcherson, Publisher Sun). Tips: The Sun 1.3 JVM has a significantly faster startup time compared to any earlier Sun release. Improve bytecode (method) execution by: using JITs; reducing (byte-)code size; profiling code to eliminate bottlenecks. Thesis Statements? Reduce garbage collection overheads by: reducing the number of write, objects generated; reusing objects; caching objects. Reduce multithreading overheads by statements for controversial targeting the granularity of locks, and managing synchronization correctly.
Other operations which improve performance include: using JAR files; using arrays rather than collections; using primitive types rather than objects. If the CPU is the bottleneck, target: code; method profiler identified bottlenecks; algorithms; and object creation. If system memory is the bottleneck, try to essay for class avoid paging by targeting: large objects; arrays; the application design. If disk I/O is the bottleneck, identify the problem and eliminate it. Ensure that you have benchmarks and targets, and thesis run reproducible benchmark tests. Target the easiest of the top 5 methods, or the top method, identified by method profiling. Thesis In India? Repeat profile, fix, benchmark iterative process. Thesis Statements For Controversial? Avoid runtime String concatenation. Use StringBuffer instead.
Local variables (method arguments and tempoararies) remain on the stack and are much faster than heap variables (static, instance new objects). Use strength reduction: x = x + 5 - x += 5; y = x/2 - y = x 1; z = x * 4 - z = x Always profile the code to find where the essay on summer vacation, bottlenecks are. equalsIgnoreCase() is faster than equals() in most cases (except where string sizes are the same). Loop backwards rather than forwards [actually its the comparison to 0 that matters]. Reduce code size by: obfuscating code; compression in jar files; excluding the thesis for controversial, manifest in jar files; reordering variable declarations; eliminating dead code; using protected methods. Manipulate data that requires parsing into a format that is for class 7, easier to thesis statements parse. Essays? Use bitshift instead of multiplying or dividing by powers of 2. Statements Issues? Use binary-And (on N-1) instead of critiquing, modulus (on N). Use Thread.sleep() instead of issues, a for loop for measured delays.
Use the update() method to draw things, not the paint() method. Use double-buffering. Apply faster algorithms and data structures. Use StringBuffer for String concatenations, rather than the '+' operator. Essay On Summer Vacation For Class 7? Use static [pre-created] exceptions. Use final classes. Javabean component architecture (Page last updated October 2001, Added 2001-10-22, Authors David Hardin and Mike Frerking, Publisher Java Developers Journal). Tips: Reusing events reduce object creation and garbage collection overheads. Passing primitive data types directly to thesis for controversial event handlers is the fastest way to how to write unit pass event information. Generic events reduce the number of (inner) classes required to thesis handle the events. The logging APIs (Page last updated September 2001, Added 2001-10-22, Author Tom Harpin, Publisher Sun).
Tips: [Article gives a high level view of the logging APIs introduced in SDK 1.4. No application is adequately deployed unless it has some performance logging in place]. The performance of games on J2ME (Page last updated March 2001, Added 2001-03-21, Author Jason R. Briggs, Publisher JavaWorld). Tips: Target performance for processors that you will run on when the project is deployed. Essays Critiquing? Implementing the ImageProducer interface and setting an image's pixels directly eliminates one or two steps in the MemoryImageSource option and seems to be about thesis for controversial issues, 10 percent to 20 percent faster on average. Raw frame rate display, without taking account of the of christmas, time taken to thesis draw an image, runs from 2 frames per second (fps) to 400 fps, depending on processor and JVM. The PersonalJava runtime has no JIT, and provides the worst performance. On Summer For Class? With a JIT it might be usable. [Article includes references to a number of hardware based Java implementations, i.e.
Java enabled CPUs.] Introductory level article on threading applets (Page last updated March 2001, Added 2001-03-21, Author Monica Pawlan, Publisher Sun). Tips: Multi-threaded programs can allow multiple activities to continue without blocking the thesis issues, user. Spawning additional threads carries extra memory and processor overhead, but can easily be worth the overheads. Write? Applets need a separate timer thread to execute any non-short tasks so that the applet remains responsive to the browser.
The volatile modifier requests the thesis, Java VM to always access the thesis, shared copy of the statements for controversial, variable so the its most current value is always read. If two or more threads access a member variable, AND one or more threads might change that variable's value, AND ALL of the threads do not use synchronization (methods or blocks) to read and/or write the value, then that member variable must be declared volatile to thesis on child rights ensure all threads see the statements for controversial, changed value. Cute tip on copy essay without unblocking a blocked socket by sending it data from thesis statements for controversial issues a timer thread. (Page last updated 1997, Added 2000-10-23, Author Albert Lopez, Publisher JavaWorld). How To? Tips: Use a separate timer thread to timeout socket operations Instead of killing the blocked socket, send it some data to unblock it. J2EE design optimizations (Page last updated September 2001, Added 2001-10-22, Author Vijay S. Ramachandran, Publisher Java Developers Journal). Tips: For data that changes infrequently (i.e. rarely enough that a user session will not need that data updating during the thesis statements issues, session lifetime), avoid transactional access by using a cached Data Access Object rather than the transactional EJB (this is called the Fast Lane Reader pattern). Don't transfer long lists of data to the user, transfer a page at essays a time (this is thesis for controversial issues, called the Page-by-Page Iterator pattern). On Child? Instead of thesis statements, making lots of remote requests for data attributes of an object, combine the attributes into application without essays another object and send the object to issues the client. How To Write? Then the attributes can be queried efficiently locally (this is called the Value Object pattern). Consider caching the value objects where appropriate. Choosing a J2EE application server, emphasizing the importance of performance issues (Page last updated February 2001, Added 2001-02-21, Author Steve Franklin, Publisher DevX).
Tips: Application server performance is statements for controversial, affected by: the JDK version; connection pooling availability; JDBC version and critiquing article optimized driver support; caching support; transactional efficiency; EJB component pooling mechanisms; efficiency of webserver-appserver connection; efficiency of persistence mechanisms. Your application server needs to statements issues be load tested with scaling, to vacation 7 determine suitability. Thesis Statements? Always validate the performance of the app server on the target hardware with peak expected user numbers. Essay? Decide on thesis statements what is acceptable downtime for your application, and ensure the app server can deliver the required robustness. High availability may require: transparent fail-over; clustering; load balancing; efficient connection pooling; caching; duplicated servers; scalable CPU support. Servlet Filters (Page last updated June 2001, Added 2001-07-20, Author Jason Hunter, Publisher JavaWorld). Tips: Servlet Filters provide a standardized technique for wrapping servlet calls. You can use a Servlet Filter to log servlet execution times [example provided].
You can use a Servlet Filter to compress the webserver output stream [example provided]. Implementing clustering on a J2EE web server (JBoss+Jetty) (Page last updated September 2001, Added 2001-10-22, Author Bill Burke, Publisher OnJava). Tips: Clustering includes synchronization, load-balancing, fail-over, and distributed transactions. [article discusses implementing clustering in an environment where clustering was not previously present]. The different EJB commit options affect database traffic and performance. Option 'A' (read-only local caching) has the smallest overhead. Hardware load balancers are a simple and fast solution to distributing HTTP requests to on child in india clustered servers. Making HTTP connections using background threads. (Page last updated September 2001, Added 2001-10-22, Author Eric Giguere, Publisher Sun). Tips: The user interface must always be responsive to the user's interaction. The application should respond to thesis statements issues input no later than a tenth of scholarship application essays, a second after it occurs: longer delays are noticed by issues the user, and make the user interface seem unresponsive.
So don't do more than about a tenth of a second's worth of work in the user-service thread in thesis on child rights in india response to any user interface event. Use separate threads to perform operations that will last longer than one tenth of a second. Provide the thesis issues, user with the option to cancel the operation at any time. [Article provides an example of making an critiquing HTTP connection following these suggestions]. Article by for controversial issues Frederic Boulanger with tuning tips. (Page last updated June 1998, Added 2000-10-23, Author Frederic Boulanger, Publisher Macadamian). Tips: Choose the essays, best algorithm or data structure. Whatever can be calculated outside of a loop should be calculated outside of the loop.
Try to for controversial minimize method calls within a loop. Reduce the thesis rights, number of references to an array in loops. Store the value of array or array elements in temporary variables and use these in the loop. For multidimensional arrays store a reference for the currently accessed row in a variable. Thesis? Store member variables in essays a local temporary variable in loops. IBM's list of Java performance tuning tips (same page, two URLs). (Page last updated 2000, Added 2000-10-23, Author ?, Publisher IBM). Thesis Statements Issues? Tips: Group native operations to reduce the number of JNI calls. Primitive types are faster than classes encapsulating types. Avoid excessive writing to essays of christmas the java console. Thesis Statements? Reorder CLASSPATH so that the most used libraries occur first. Scholarship Application Without Essays? Don't overuse synchronized methods.
Use int instead of long when possible. When possible, declare methods as final. If needed, only call the garbage collector explicitly at an appropriate time (when things are quiet). Prudent use of zip and jar formats can improve load time. Compile java files with the optimizer on. Cache frequently used objects when possible. Use static final when creating constants. Statements? Use StringBuffer when doing excessive string manipulations. Consider when to use local variables in critiquing loops (speed vs. memory?).
Vectors are more flexible than arrays, but much slower. For Controversial? It is faster to on child in india add/delete items from the end of the vector. Avoid unnecessary casts and for controversial instanceof. Scope of variables can impact performance. EJB2.0 Container-Managed Persistence (Page last updated July 2001, Added 2001-08-20, Author Beth Stearns, Publisher Sun).
Tips: EJB 2.0 Container-Managed Persistence provides local interfaces which can avoid the performance overheads of remote interfaces. FAQ site with a couple of basic performance tips. (Page last updated 2000, Added 2000-10-23, Author Martin Webb, Publisher IRT). Tips: FAQ 4002: Use an ImageObserver (method listed in thesis on child FAQ) to statements issues control how and when images are painted during loading. FAQ 4003: Minimise flicker in animations by overriding update() to simply call paint() (default action is to clear the image first), and use double buffering. FAQ 4063 4066: Use jar files to reduce the amount of time that it takes to download an applet. Anonymous inner classes (Page last updated December 2000, Added 2002-04-26, Author Heinz M. Kabutz, Publisher Kabutz).
Tips: Accessing private data members of an outer class, is done using a generated method, which is slower than normal field access. Though HotSpot can inline the access. Minimizing space taken by scholarship application without essays HTTP downloads (Page last updated October 2001, Added 2001-10-22, Authors Gary Adams and Eric Giguere, Publisher Sun). Tips: Use HttpConnection.getLength() to determine the number of bytes needed to thesis for controversial to hold the without essays, data from a download. Issues? Use a ByteArrayOutputStream to accumulate results if the content length is indeterminate. The best performance is essays of christmas, obtained from a 1.1 compliant webserver using persistent connections. Double-if on multi-CPU (Page last updated February 2002, Added 2002-03-25, Author Phil Vickers, Publisher IBM). Thesis Issues? Tips: Double-if logic fails on multiple CPU machines. You need to synchronize around double-if logic for consistent results, though this may be inefficient.
Faster JSP with caching (Page last updated May 2001, Added 2001-05-21, Author Serge Knystautas, Publisher JavaWorld). Tips: The (open source) OSCache tag library provides fast in-memory caching. Cache pages or page sections for essay vacation for class, a set length of time, rather than update the page (section) with each request. Caching can give a trade-off between memory usage and CPU usage, especially if done per-session. Thesis Statements Issues? This trade-off must be balanced correctly for optimal performance. Scaling web services (Page last updated June 2001, Added 2001-07-20, Author Simeon Simeonov, Publisher XML Developers Journal). Tips: Use bigger, better, faster hardware, but there is a limit to the scalability of a single server: most application performance does not scale linearly with increases in the hardware power. Use more than one server in copy without a cluster that services requests as if it were a single server using: OS-level clustering (OS level built in failover mechanisms); Software load balancing (using a loda-balancing front-end dispatcher); Hardware load balancing (e.g.
DNS round-robin to different servers). A basic load-balancing scheme is achievable by sending documents with different binding addresses (differnent URL hosts) Use faster communication protocols (e.g. plain sockets) Support asynchronous request processing message based interactions. Multithreaded Swing Applications (Page last updated September 2001, Added 2001-10-22, Author Monica Pawlan, Publisher Sun). Tips: Use the SwingUtilities.invokeAndWait() and thesis issues SwingUtilities.invokeLater() methods to put code on the GUI eventr queue. Vacation 7? Spawn threads for statements for controversial, long operations so that the copy essay without, user does not get a blocked GUI.
Timers and low-level GUI display effects (Page last updated September 2001, Added 2001-10-22, Author Roman Bialach, Publisher Micro Java). Tips: You need a scheduling mechanism to perform animation, scrolling, updating the display, etc. The paint() method on the Canvas is called by the system only if it thinks that it needs to repaint it. So we need another timer to thesis statements for controversial repaint the essay on summer, screen on a regular basis. Use a timer to periodically call repaint(). Architecting and Designing Scalable, Multitier Systems (Page last updated August 2001, Added 2001-10-22, Author Michael Minh Nguyen, Publisher Java Report).
Tips: Separate the UI controller logic from the servlet business logic, and let the thesis statements, controllers be mobile so they can execute on essay vacation 7 the client if possible. Validate data as close to the data entry point as possible, preferably on the client. This reduces the network and server load. Business workflow rules should be on the server (or further back than the front-end). You can use invisible applets in a browser to validate data on the client. Sun community discussion on Optimizing Entity Beans with Akara Sucharitakul (Page last updated June 2001, Added 2001-07-20, Author Edward Ort, Publisher Sun).
Tips: Prepared SQL statements get compiled in the database only thesis for controversial issues, once, future invocations do not recompile them. The result of this is a decrease in the database load, and an increase in performance of up to essay without 5x. Container Managed Persistence (CMP) can provide 2-3x better performance than Bean Managed Persistence (BMP). Optimizing dynamic web pages (Page last updated July 2001, Added 2001-07-20, Author Helen Thomas, Publisher Java Developers Journal). Statements For Controversial? Tips: Dynamic generation of essays of christmas, web pages is more resource intensive than delivering static web pages, and thesis can cause serious performance problems. Dynamic web page generation incurs overheads from: accessing persistent and/or remote resources/storage; data formatting; resource contention; JVM garbage collection; and script execution overheads. Dynamic content caching tries to mitigate Dynamic web page generation overheads by reusing content that has already been generated to service a request. JSP cache tagging solutions allow page and copy fragment level JSP output to be automatically cached.
On highly personalized sites page-level caching results in low cache hit rates since each page instance is unique to statements for controversial issues a user. Component-level caching applies more extensively when components are reused in copy essay many pages, but requires manual identification of bottleneck components. J2ME apps, with a discussion of the needs to balance performance (Page last updated June 2001, Added 2001-07-20, Author Glenn Coates, Publisher Java Developers Journal). Thesis Statements For Controversial Issues? Tips: J2ME devices have limited processing power, so performance is important and 7 must be considered for statements issues, the target device. Essays Of Christmas? JIT compiled or natively compiled code is preferred, but may be unobtainable because of memory resource or deployment considerations.
JVM Interpreters have a significantly lower memory overhead compared to JIT/HotSpot JVMs, but are much slower. Selectively compiled code might provide a good compromise of speed and memory if deployment considerations allow. The application does not need to be lightning fast in statements for controversial issues order to have a responsive user interface. The perception of speed is important, for on summer vacation 7, example, the user interface should give immediate feedback. JVM slection for the J2ME device is thesis statements for controversial, pivotal to achieving the required performance. Compared to desktop environments, embedded systems typically have: lower memory availability; less processing power; user Interface restrictions; reduced communication bandwidth or unreliable connections; battery power; higher reliability requirements; lack of a file system. Tuning JVMs for servers. (Page last updated February 2002, Added 2002-03-25, Author Timothy Dyck, Publisher E-Week).
Tips: Multiple JVMs are often available for a particular platform. Choose the JVM that best suits your needs. The test here found setting min and max heaps to the same value provided the best performance. Limiting each Sun 1.3 JVM to using two CPUs (test used multiple JVMs and essay for class 7 6 CPUs) provided a 30% reduction in thesis statements CPU usage. IBM JVMs did not require (or benefit from) this optimization. Data compression (Page last updated December 2001, Added 2001-12-26, Author Tony Sintes, Publisher JavaWorld).
Tips: [Article covers how to add zip compression to rights in india RMI communications]. Creating Web-based, interactive graphics. (Page last updated December 2001, Added 2001-12-26, Author Steve Lloyd, Publisher DevX). Tips: If an applet parameter's [tags in the webpage] length is too long, the Web page's responsiveness begins to for controversial issues bog down. Move all but the essential parameters from the APPLET tag to a dedicated HTTP link between the essays of christmas, applet and the servlet. This allows page loading and applet initialization to occur at the same time over separate connections. Close java.sql.Statements when finished with. Inverting booleans (Page last updated February 2002, Added 2002-03-25, Author Heinz M. Kabutz, Publisher Kabutz). Thesis Statements? Tips: The fastest way to invert a boolean is to XOR it (bool ^= true). Be careful when making performance measurements with HotSpot because the optimizing compiler can kick in to adjust results. The Proxy design pattern. (Page last updated February 2002, Added 2002-03-25, Author David Geary, Publisher JavaWorld).
Tips: Creating images is essays, expensive. ImageIcon instances create their images when they are constructed. If an application creates many large images at once, it could cause a significant performance hit. If the application does not use all of its images, it's wasteful to create them upfront. Using a proxy, you can delay image loading until the image is required. The Proxy pattern often instantiates its real object, the Decorator pattern (which can also use proxy objects) rarely does. The java.lang.reflect package provides three classes to support the Proxy and Decorator patterns: Proxy, Method, and statements for controversial InvocationHandler. Stateful vs Stateless EJBs (Page last updated May 2001, Added 2001-05-21, Author Chuck Caveness, Doug Pardee, Publisher IT World). Article? Tips: Stateless session beans can support multiple clients, thus increasing scalability.
Webservices SOAP communications overheads (Page last updated January 2002, Added 2002-02-22, Author Leigh Dodds, Publisher XML). Issues? Tips: Generating XML produces a large amount of data during communications, but this does not mean that the communication will be the bottleneck. Webservices have all the same limitations of every other remote procedure calling (RPC) methodology. Requiring synchronous communications across a WAN is a heavy overhead regardless of the protocol. Unit? If Web services tend to thesis issues be chatty, with lots of on child, little round trips and a subtle statefulness between individual communications, they will be slow. That's a function of failing to realize that the issues, API call model isn't well-suited to building communicating applications where caller and callee are separated by a medium (networks!) with variable and unconstrained performance characteristics/latency. Asynchronous messaging may be required for efficient webservices.
Sun community chat session on Threading and essays of christmas Concurrency in the Java Platform with Thomas Christopher and George Thiruvathukal (Page last updated January 2001, Added 2001-02-21, Author Edward Ort, Publisher Sun). Tips: If memory is at a premium, the cost of allocating a Thread object and allocating a stack can be expensive. If there are real-time considerations, you do not have any scheduling and performance guarantees for threads. Issues? Be careful about the number of threads you create: too many and essay without you can exhaust your memory: too few and for controversial you don't get the copy without, advantages of parallelism. Use javax.swing.SwingUtilities.invokeLater() [java.awt.EventQueue.invokeLater()] to schedule work onto the awt thread. Basic article on thesis statements for controversial issues a minimal ArrayList implementation, from a micro-Java slant (Page last updated March 2001, Added 2001-04-20, Author Lee Miles, Publisher Micro Java).
Tips: ArrayLists are the fastest SDK collection class. Essays Of Christmas? System.arraycopy provides an efficient method for copying arrays. You should request garbage collection whenever elements are dereferenced (e.g. the statements for controversial issues, list is cleared). Precompiling JSPs (Page last updated July 2002, Added 2002-07-24, Author Steve Mueller, Scot Weber, Publisher Weblogic Developers Journal). Tips: Precompile your JSPs one way or another to essay on summer for class avoid the first user having a slow experience. High performance inserts with DB2 and JDBC (Page last updated April 2002, Added 2002-07-24, Author Krishnakumar Pooloth, Publisher IBM). Tips: Use SQLJ to thesis get the use of buffered inserts, and modify the code generated from on summer vacation 7 SQLJ to reuse the RTStatement object. Optimizing StringBuffer usage (Page last updated May 2001, Added 2001-05-21, Author Glen McCluskey, Publisher Sun). Issues? Tips: Pre-size the StringBuffer to the expected result String size where possible. Customized high-speed, fine-grained access control (Page last updated September 2001, Added 2001-10-22, Author Wally Flint, Publisher JavaWorld). Essays? Tips: [Article discusses an Access control pattern which has no performance penalty].
Connection Pooling with JRun (Page last updated June 2001, Added 2001-08-20, Author Karl Moss, Publisher Allaire). Tips: Establishing an initial connection is statements for controversial, one of the most expensive database operations. Use a pool of thesis, connections that are ready and waiting for use to minimize the connection overhead. Thesis For Controversial? Connection pooling is one of the largest performance improvements available for applications which are database intensive. Connections should timeout if not used within a certain time period, to reduce unnecessary overheads. Article? Initial and maximum pool sizes provide further mechanisms for for controversial issues, fine-tuning the pool. JDBC 2.0 supports connection pooling, though a particular driver may or may not use the support. If pooling is supported by the driver, it is probably more efficient than a proprietary pooling mechanism since it can leverage database specific features. Some IBM Java performance tips. Although intended for AS/400 Java, many tips are generally applicable (Page last updated ?, Added 2000-10-23, Author ?, Publisher IBM).
Tips: Minimize the use of synchronized methods. Use the -O javac option. Minimize object creation, reuse objects. Use StringBuffers or char arrays to minimize the number of String objects created. On Summer Vacation For Class? Use faster accesses. Accesses from fastest to slowest: local variable; instance variable: accessor method in-lined; accessor method; synchronized accessor method.
Minimize the use of created exceptions. Use static final when creating constants. Use Prepared Statements. Store character data in DB2 as Unicode, numeric data as float. Monitoring Networked Applications (Page last updated March 2002, Added 2002-04-26, Author Russ Currie, Publisher Message MQ). Tips: Use network probes to thesis statements for controversial break down how the network is being used by the various networked applications on it.
Deciding whether EJB is appropriate. (Page last updated September 2001, Added 2001-10-22, Author Ed Roman, Publisher The Server Side). Tips: An HTTP layer is not always necessary. Connecting directly to EJBs is faster and provides automatic load balancing. Tips on using XSLT (Page last updated August 2001, Added 2001-10-22, Author Eric M. Essays? Burke, Publisher O'Reilly). Tips: XSLT transformations are CPU memory intensive, so cache results wherever possible.
Examples include stylesheets; mainly static XML data (cache the transformation result). Rambling discussion of building J.Crew website, in Chapter 3 of J2EE Technology in thesis statements issues Practice (Page last updated September 2001, Added 2001-10-22, Authors Dao Ren, Dr. Rick Cattell and essays of christmas Jim Inscore, Publisher Sun). Statements Issues? Tips: Use database connection pooling Cache Database Requests [Statistics useful for comparison if you are building a business enterprise site: The architecture can handle 8,000 concurrent user sessions; 85 dynamic page views a second; 250,000 unique daily visitors; 8 million hits a day; 1 to 2 second average response time]. Converting booleans to strings. (Page last updated November 2001, Added 2001-11-27, Author Tony Sintes, Publisher JavaWorld). Tips: Use String.valueOf(bool) to convert booleans to strings. Generating integer random numbers (Page last updated September 2001, Added 2001-10-22, Author John Zukowski, Publisher Sun). Tips: [Article explains why ways of generating random integers produces skewed results. Of Christmas? Important for statements, correctly simulating a variety of things].
Tuning tips intended for Sun's Web Server product, but actually generally applicable. (Page last updated 1999, Added 2000-10-23, Author ? - a Sun document, Publisher Aikido). Tips: Use more server threads if multiple connections have high latency. Use keep-alive sockets for higher throughput. Essays Article? Increase server listen queues for high load or high latency servers. Avoid or reduce logging. Buffer logging output: use less than one real output per log. Issues? Avoid reverse DNS lookups. Write time stamps rather than formatted date-times. Critiquing Article? Separate paging and application files. For Controversial Issues? A high VM heap size may result in copy essay without paging, but could avoid some garbage collections. Thesis Statements For Controversial? Occasional very long GCs makes the VM hang for essays, that time, leading to variability in service quality.
Doing GC fairly often and avoiding paging is statements issues, more efficient. Security checks consume CPU resources. You will get better performance if you can turn security checking off. Research paper on high performance Java. (Page last updated 1999, Added 2000-10-23, Author Sandeep K. On Summer Vacation For Class 7? Singhal, Publisher IBM). Tips: Use local variables as a first choice for issues, manipulating data. Essay 7? Rewrite the thesis issues, loop test so that it uses a comparison to 0. Avoid synchronization where possible. How To Unit? Reuse and pool objects.
Avoid throwing exceptions ( not avoid using try-catch blocks). Build specialized classes, don't rely on the general-purpose (but slow) core SDK library. Use a zip archive to download classes. (Page last updated 1997, Added 2000-10-23, Author John D. Mitchell, Publisher JavaWorld). Tips: Use a zip archive to download classes. JMS CORBA (Page last updated December 2001, Added 2001-12-26, Author Steve Trythall, Publisher OnJava). Tips: Asynchronous messaging is a proven communication model for developing large-scale, distributed enterprise integration solutions. Messaging provides more scalability because senders and receivers of messages are decoupled and thesis are no longer required to execute in critiquing article lockstep. Wrapping PreparedStatement (Page last updated January 2002, Added 2002-02-22, Author Bob Byron and Troy Thompson, Publisher JavaWorld).
Tips: With Statement, the same SQL statement with different parameters must be recompiled by thesis statements for controversial the database each time. But PreparedStatements can be parametrized, and essays these do not need to be recompiled by the database for use with different parameters. [Article discusses a PreparedStatement wrapper class useful for debugging.] String to double (Page last updated September 2001, Added 2001-10-22, Author Tony Sintes, Publisher JavaWorld). Tips: Use Double.parseDouble() instead of Double.valueOf(aString).doublevalue() . Tutorial on for controversial issues non-blocking socket I/O available from essay on summer for class 7 JDK 1.4 (Page last updated September 2001, Added 2001-10-22, Author Tim Burns, Publisher Owl Mountain). Tips: [No tips, and a rather haphazard tutorial but beggars can't be choosers]. Sun community chat session with Bill Shannon, Kevin Osborn, and Jim Glennon on JavaMail (Page last updated December 2000, Added 2001-01-19, Author Edward Ort, Publisher Sun). Statements Issues? Tips: You might see a performance increase by using multiple connections to your mail server.
You would need to get multiple Transport objects and call connect and sendMessage on each of essays, them, using multiple threads (one per connection) in your application. JavaMail 1.2 includes the thesis for controversial issues, ability to set timeouts for 7, the initial connection attempt to the server. JavaMail tries to allow you to make good and efficient use of the IMAP protocol. Fetch profiles are one technique to allow you to get batches of information from the thesis statements issues, server all at once, instead of single pieces on demand. Used properly, this can make quite a difference in 7 your performance. Optimizing recursive methods (Page last updated June 2001, Added 2001-06-18, Author Eric E. Thesis Statements? Allen, Publisher IBM). Tips: Try to convert recursive methods into tail-recursive methods. You can test if a particular JIT is able to convert tail-recursive into without loops with a dummy tail-recursive method which never terminates.
If the JVM crashes because of stack overflow, no conversion is done (if the conversion is managed, the statements for controversial issues, JVM loops and never terminates). The HotSpot JVM with the 1.3 release does not convert tail-recursive methods into loops. The IBM JVM with the essays, 1.3 release does. Java collections (Page last updated June 2001, Added 2001-06-18, Author Richard G. Statements? Baldwin, Publisher EarthWeb). Tips: Choose the right structure for the right job. ArrayList may be faster than TreeSet for some operations, but ArrayList.contains() requires a linear search (as do other list structures) while TreeSet.contains() is a simple hashed lookup, so the latter is much faster. The facade pattern for essays, internationalization (Page last updated October 2001, Added 2001-10-22, Author David Gallardo, Publisher Java Developers Journal). Tips: If multiple strings will be compared using internationalized comparison, use (and reuse) CollationKeys to thesis statements for controversial issues manage the without essays, comparisons during sorting. Computational planning and statements for controversial issues scheduling problem solving (not performance tuning) (Page last updated June 2001, Added 2001-06-18, Author Irvin Lustig, Publisher Java Developers Journal). Tips: [Article introduces the copy essay without, solving of planning and statements scheduling problems in Java]
Various tips. Critiquing? For web servers? (Page last updated 2000, Added 2000-10-23, Author ?, Publisher ?). Tips: Test multiple VMs. Tune the thesis, heap and stack sizes [by trial and error], using your system memory as a guide to upper limits. Keep the system file cache large. [OS/Product tuning, not Java] Compression uses significant system resources. Don't use it on a server unless necessary. Essay Without? Monitor thread utilization. Increase the number of threads if all are heavily used; reduce the number of threads if many are idle.
Empirically test for issues, the optimal number of database connections. Optimizing padded string display (Page last updated June 2002, Added 2002-07-24, Author Gervase Gallant, Publisher JavaZoid). Tips: Avoid copying individual string characters. Use the same underlying char array, by using methods like String.substring(). Runtime.exec() pitfalls (Page last updated December 2000, Added 2002-07-24, Author Michael C. Daconta, Publisher JavaWorld). Essay 7? Tips: Runtime.waitFor blocks until the statements, spawned process terminates. Avoid blocking the Java thread because the spawned process is in india, waiting on for controversial issues I/O. Make sure you read and write the spawned process's I/O as required. A worked example of optimizing Lava Rocks Java Printf. (Page last updated 1999, Added 2000-10-23, Author ?, Publisher SharkySoft). Tips: When adding multiple items to a collection, add them all in one call if possible.
Avoid creating multiple objects where they can be replaced by one object referred to many times. Avoid repeatedly executing a parse [or other constant expression] in a loop when the execution can be achieved once outside the loop. Application Without Essays? Call more complex underlying methods instead of thesis for controversial, simpler wrapping methods. JMS redelivery (Page last updated March 2002, Added 2002-03-25, Author Prakash Malani, Publisher JavaWorld). Tips: Both auto mode (Session.AUTO_ACKNOWLEDGE) and essays critiquing duplicate delivery mode (Session.DUPS_OK_ACKNOWLEDGE) guarantee delivery of thesis issues, messages, but duplicate okay mode can have a higher throughput, at the cost of the occasionally duplicated message. The redelivery count should be specified to avoid messages being redelivered indefinitely. Java I/O tutorial by essays of christmas Elliotte Rusty Harold (author of statements for controversial, O'Reilly's Java I/O book). (Page last updated November 2000, Added 2001-01-19, Author Elliotte Rusty Harold, Publisher IBiblio). Tips: Sometimes output streams are buffered by the operating system for essays critiquing, performance. The flush() method forces the data to be written whether or not the buffer is full. This is not the same as the buffering performed by a BufferedOutputStream. That buffering is handled by the Java runtime.
This buffering is at the native OS level. However, a call to flush() should empty both buffers It's more efficient to for controversial issues read multiple bytes at thesis on child in india a time, i.e use read(byte) rather than read(). Thesis Statements Issues? The best size for the buffer is highly platform dependent and generally related to the block size of the disk, at least for file streams. Less than 512 bytes is probably too little and more than 4096 bytes is probably too much. Ideally you want an essays of christmas integral multiple of the block size of the thesis for controversial, disk. However, you should use smaller buffer sizes for unreliable network connections. iPlanet Web Server guide to servlets, with a section at the end on Maximizing Servlet Performance. (Page last updated July 2000, Added 2001-02-21, Author ?, Publisher Sun). Tips: Try to how to write optimize the thesis statements for controversial issues, servlet loading mechanism, e.g. by listing the servlet first in loading configurations. Tune the heap size. Keep the classpath short. Paul Tyma's article on essays low level Java optimizations. Statements Issues? (Page last updated 1996, Added 2000-10-23, Author Paul Tyma, Publisher Dr.
Dobb's). Tips: Speed up the essays, most-used code, such as highly iterated loops and popularly called methods. int is faster than long Performance of code that is heavily dependent upon system API calls is largely out of your hands. Create classes that support primitive data types directly, rather than having to wrap the data, e.g. a Stack class that directly stores int s. Inline code. Thesis Statements For Controversial Issues? Declare methods as static or private to allow inlining. Apply code motion (eliminating redundant calculations).
Improving applet download time by copy without installing the applet on the client. (Page last updated 1997, Added 2000-10-23, Author Mark Roulo, Publisher JavaWorld). Tips: Store your applet on the client machine so that applet download time is absolutely minimal. This is not worth doing for really small applets. Sun community chat on iPlanet (Page last updated November 2001, Added 2001-12-26, Author Edward Ort, Publisher Sun). Tips: Optimal result caching (caching pages which have been generated) needs tuning, especially the timeout setting. Make sure the timeout is thesis statements, not too short. Developing Scalable Distributed Applications (Page last updated August 2001, Added 2001-10-22, Author Mario A. Torres, Publisher Dr. Dobb's). Tips: Use interfaces. Alot.
Inner classes (Page last updated August 2001, Added 2001-10-22, Author Tony Sintes, Publisher JavaWorld). Tips: Nonstatic member classes must maintain a reference to the enclosing instance, which adds overhead, so use static inner classes where no acces is need to the enclosing instance. Basic performance tuning intro (Page last updated March 2000, Added 2001-03-21, Author Reggie Hutcherson, Publisher JavaWorld). On Child Rights In India? Tips: Use a JIT-enabled JVM or HotSpot. JyLog logger (Page last updated December 2001, Added 2001-12-26, Author Sanjay Dahiya, Publisher JavaWorld). Tips: Using JyLog (which uses the JPDA) slows down the JVM executuion time: use standard logging, not JyLog, for deployed applications. Using Timers (java.util.Timer) (Page last updated April 2001, Added 2001-04-20, Author Eric Giguere, Publisher Sun). Thesis Issues? Tips: Timers provide a simple mechanism for repeatedly executing a task at a set interval [with simplicity being the keyword here. Don't look for anything sophisticated like thread interrupt control]. Article on high availability architecture. Article? If the system isn't up when you need it, its not performing. (Page last updated November 1998, Added 2000-10-23, Author Sam Wong, Publisher Sun).
Tips: Eliminate all potential single-points-of-failure, basically with redundancy and automatic fail-over. Consider using the redundant components to for controversial improve performance, with a component failure causing decreased performance rather system failure. Another use StringBuffer instead of '+' tip. (Page last updated Jul 1999, Added 2000-10-23, Author Real Gagnon, Publisher EarthWeb). Tips: use StringBuffer instead of '+'. Tuning the SPECjbb2000 Java specmark. (Page last updated 2000, Added 2000-10-23, Author ?, Publisher SPEC). Tips: Use Java profilers (-prof, -Xrunhprof) to determine the routines most heavily used. Having extra stuff in CLASSPATH can degrade performance on unit some JVMs. Microsoft discussion about for controversial, csharp garbage collection (the Java clone unsurprisingly has similar issues) (Page last updated October 2001, Added 2001-10-22, Author Brian Harry, Publisher Harry). Tips: [No performance tips here. But a fascinating discussion about copy without, all the thought that has gone in to csharp GC, only to result in a what already exists in Java]. Sun system (not Java) profiling with Sun WorkShop. (Page last updated 1998, Added 2000-10-23, Author ?, Publisher Sun).
Tips: Select the right combination of compiler options, optimized libraries, and coding techniques. Compiler optimizations: common subexpression elimination; loop-invariant hoisting; strength reduction; dead and redundant code elimination; loop pipelining/unrolling; instruction scheduling; inlining; code motion; profile feedback; tail recursion elimination; loop parallelization; loop interchange; loop fusion (combining loops to thesis statements issues reduce overhead). Cache blocking: a technique that increases the cache-hit rates of the program by increasing the reuse of the on summer, data present in the cache. (Page last updated , Added 2002-10-30, Author , Publisher ). Thesis? Tips: x.
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My Libertarianism.org Essays: A Third Anniversary Cerebration. Smith marks three years of his essays with some thoughts about the importance of libertarian theory and history. My first Libertarianism.org essay was posted on November 3, 2011, and statements for controversial issues, this essay is #150 in an ongoing series with no end in sight. The fact that I have had no trouble coming up with topics relating to libertarian ideas, especially as manifested in the history of write, political thought, and the fact that I cannot imagine ever running out of thesis statements, topics, testify to the richness and diversity of the libertarian tradition. I am taking this break from essays critiquing article my current series, “Self-Interest and Social Order in Classical Liberalism,” in order to thesis for controversial issues offer some reflections on the importance of ideas in general and on the history of libertarian ideas in particular. Since my essays are aimed at how to unit a general audience rather than academics and specialists, a question naturally arises: Why should libertarians care about the thesis for controversial philosophy and history of their own political ideology? In addressing this question here I am in a sense carrying coals to Newcastle, since anyone who reads my essays on a regular basis is already interested in essays these matters. Moreover, I don’t think every libertarian necessarily should take an active interest in the philosophical and for controversial, historical foundations of libertarianism.
As in any broad-based movement, specialization and how to unit, the division of labor have occurred in the libertarian movement, with some participants more focused than others on practical, day-to-day political issues. Statements? All this is normal and unobjectionable, of course, but it would be a serious mistake to suppose that knowledge of the theory and history of libertarian ideas is without practical value. Let’s take a look at this issue in more detail. Perhaps the most dramatic difference in libertarian thinking about strategy is write that between pragmatists and ideologues. I offer these categories as ideal types or pure forms (to use the thesis statements issues sociological terms of Max Weber and Georg Simmel). In other words, I have constructed these ideal types for copy essay, the purpose of analysis, without suggesting that real libertarians fall exclusively into one category or the thesis issues other. Most of us probably embody some features of both types, with a disposition to favor one over the other. Moreover, “pragmatist” and essay without, “ideologue” are relative terms; even the most practical of libertarian pragmatists may be regarded as an statements issues, impractical ideologue by the general public. Pragmatists typically pride themselves on their “common sense” and on their “realistic” view of the political world. Although they do not altogether deny the importance of theory and ideology, pragmatists believe that these have little application outside the immediate circle of hard-core libertarians. Libertarians may enjoy debating the fine points of theory among themselves, but this intellectual recreation cannot help us in the rough and tumble world of application without essays, politics.
The pragmatist sees himself as a problem-solver; he is going to thesis statements for controversial roll up his sleeves and get something done. The pragmatist is especially fond of copy essay, talking about “the real world”—a place, he thinks, that ideologues rarely visit and know little about. The real world is the world of flesh-and-blood human beings, the domicile of the proverbial “average person,” in contrast to the abstract world of the libertarian theorist. The pragmatist, however much he may disparage theory, often has a rather elaborate theory about how to change the world. If he has a background in business (which he often does), the pragmatist will wax eloquent on how libertarian ideas can be “packaged” and thesis issues, “sold.” The average person, he tells us, doesn’t want to hear about application rights and the proper role of government; he is interested only in thesis statements his family, his job, and his bank account. Essay Vacation 7? It is the pragmatist who likes to write and read books with titles like How You Can Profit from the statements Coming Extinction of the Human Race. We also have the pragmatic activist who is suspicious of abstract ideology and believes that he has his finger on the pulse of people in the real world. Radical ideas and causes, according to this activist, will alienate our potential supporters, many of whom are disenchanted with traditional politics.
Therefore, we are cautioned not to focus on unpopular issues, such as drug legalization. There are many permutations of pragmatism, some of which are more sophisticated than the types presented here, but all share a dislike, or at least a strong suspicion, of libertarian ideologues and essay 7, their abstract arguments. When the libertarian pragmatist speaks of “facts” and for controversial issues, the “real world,” he means the scholarship application essays knowledge gained through experience and observation, knowledge acquired from specific events and circumstances. For Controversial Issues? He begins with empirical facts (concrete people, specific actions, etc.) and scholarship without, then generalizes about issues strategy, based on what libertarians can realistically hope to achieve in the near future. This inductive process is based on the historical method. All facts appealed to by the thesis pragmatist (assuming they are accurate) fall within the thesis statements for controversial issues domain of historical knowledge. History is the study of past human actions; it is concerned with the unique individual event, not with a general pattern or theory. Without? These historical events are what pragmatists call the thesis statements “real world” of facts. Ironically, the without pragmatist sometimes places history in the same category as theory, relegating both to the ethereal world of the ideologue, scholar, and academic. Yet, as Mises and others have pointed out, all human knowledge falls into one of these two categories. Knowledge of particular concrete facts is thesis statements always knowledge of something that has already taken place; this is historical knowledge.
General knowledge, on the other hand, does not refer to a specific time and place; this is theoretical knowledge. All knowledge refers either to specific phenomena that occurred at a determinate time and place in the past, or to general propositions that are abstracted from any particular time and place. On Child? The former is the sphere of history; the latter is the sphere of theory. The pragmatist commits himself to a strategic method based on history instead of theory. This is a plausible choice, provided the pragmatist understands the method he is using, especially its limitations. But this rarely happens.
The pragmatist who disdains theory fails thereby to reflect on thesis statements issues the theoretical premises and implications of his own method, which remain unacknowledged, unappreciated, and often ill-treated. I will discuss three aspects of this problem. (1) The failure to analyze methodological assumptions is thesis clearly illustrated by the mole-like historical sight of some pragmatists who, in their search for empirical data, search no farther than their immediate range of vision. Statements? History, for the mole, is limited to what he has personally witnessed or at least to events that have occurred during recent decades. For the mole, history began a decade ago, possibly two or three, but rarely does the mole regard as relevant any event that is older than he is. His life and essays article, memory, it seems, just happen to overlap perfectly with the only period of history that he needs to thesis for controversial know. By a convenient coincidence, all relevant facts pertaining to a free society and how to achieve it are confined to vacation the same period of time in which the pragmatist has been interested in libertarianism.
Given his commitment to the real world, the pragmatist should immerse himself in a study of the real world (i.e., history) and learn what factors have contributed to freedom over the past 2500 years. Modern libertarians are not the first people to statements value liberty, nor are we the copy most successful. Seventeenth- and eighteenth-century libertarians, for example, faced even greater odds than we do, yet they had spectacular triumphs in some areas, such as religious freedom. Those successes were not accidental. Thesis For Controversial Issues? Early libertarians were acutely aware of strategic issues—witness the popular appeal of the Enlightenment philosophes , who devoted a good deal of thought to how to reach a general public—yet many of essay, these early libertarians, because of their acute interest in theory and thesis issues, the history of essay vacation for class 7, ideas, would qualify as ideologues by the standards of the modern pragmatist.
Indeed, the very word “ideologue” was coined by for controversial, the pragmatic Napoleon, who used it to smear Benjamin Constant and other French libertarians who refused to sacrifice principles to expediency, and who demanded a philosophical justification for copy, the immense power wielded by Napoleon. I agree with the pragmatist that we should be concerned with what will work in statements for controversial issues the real world. But this requires that we learn something about the real world, which is far more complex than the mole would have us believe. Essays? If we want to know what will work , we should find out what has worked in statements for controversial issues the past. Therefore, the sincere pragmatist, before he trashes ideologues, should study history for essay, ten years or so, reflect on what he has read, and then get back to us. (2) The most serious error of pragmatism is its lack of appreciation for the role of ideology in social perception. By “social perception” is meant how we “perceive” the thesis statements for controversial world of social wholes (or entities), such as “state,” “society,” “church,” and “the market.” In truth, we do not perceive social entities with our eyes; rather, we understand them with our minds. Social entities, as Hayek said, are “constituted” by the mind.
They are not physical things, like rocks and trees and thesis on child in india, birds, but are mental constructs of abstract relationships. This means that how we think about social entities will greatly influence how we perceive them. We libertarians know this from experience, having encountered many people who appear to thesis “see” government differently than we do. Some people don’t see government as essentially coercive; they may even see taxes as voluntary. These differences in social perception result from viewing social reality through different ideological lenses. Ideology is absolutely essential to copy essay the success of the libertarian movement, because it establishes a common frame of reference. If we fail to convince the average person, this is often because we see a different social reality than does the average person. Before we can convince other people we must be referring to the same social world. The real world of social interaction is not merely a world of objective data and physical entities.
It is largely a subjective world, one that is filtered through ideological assumptions, premises, and prejudices. The social world is constituted by the ideas that people have about it. For Controversial? If libertarians can change those ideas, they can, in a very literal sense, change the essays of christmas world. (3) In evaluating any form of pragmatism, we should keep in mind that the greatest benefits of a free society are often those that cannot be foreseen or predicted. Statements For Controversial? As Hayek pointed out, this has important implications for any pragmatic strategy. Copy Essay? As he wrote in Law, Legislation, and Liberty : “Since the value of freedom rests on the opportunities it provides for unforeseen and unpredictable actions, we will rarely know what we lose through a particular restriction of statements issues, freedom.” The direct effects of market intervention, including its apparent short-term benefits, will be apparent in many cases, but we cannot know all the critiquing opportunities that have been lost through such intervention. This means that liberty will tend to lose out in many cost-benefit analyses, because the benefits of intervention can be “seen,” while the costs, the unrealized opportunities, remain largely “unseen” (to use Bastiat’s terms). Consequently, whenever policy decisions are based on expediency instead of principle, “freedom is bound to be sacrificed in almost every instance.” Hayek continued:
The preservation of a free system is so difficult precisely because it requires a constant rejection of measures which appear to be required to secure particular results, on no stronger grounds than that they conflict with a general rule, and frequently without our knowing what will be the costs of not observing the rule in the particular instance. A successful defense of freedom must therefore be dogmatic and make no concessions to expediency….Freedom will prevail only if it is accepted as a general principle whose application to particular instances requires no justification. Modern libertarian theory is steeped in the revolutionary ideology of the thesis statements for controversial issues seventeenth and essays critiquing article, eighteenth centuries; of this there can be no doubt. Thesis Statements Issues? It was mainly from write British writers like Algernon Sidney, John Locke, and thesis statements, Trenchard and Gordon (the authors of Cato’s Letters ) that eighteenth-century Americans learned their revolutionary catechism. Libertarians are generally aware of their revolutionary heritage. What they sometimes fail to appreciate, however, is how detailed and thesis, specific our ideological ancestors were about thesis for controversial some key features of libertarian theory. Essay Vacation? In some cases they explored the theory of liberty in greater detail than have present-day libertarians, but some of their insights have unfortunately been lost or ignored by the modern movement.
Having immersed myself for many years in the libertarian literature of the seventeenth and for controversial issues, eighteenth centuries, I sometimes forget that my enthusiasm is not shared by write, every libertarian. I am quite astonished when I recall that some dedicated libertarians have never even read John Locke, even though his Second Treatise of Government is arguably the most important and influential book on statements liberty ever written. I recommend that you read such people, not because they will increase your knowledge of history—though there is certainly nothing wrong with that—but because they will increase your knowledge of liberty. Much of what early philosophers of liberty had to say is of practical value to modern libertarians. As noted previously, our forefathers and foremothers faced even greater odds than we do, yet their efforts to establish liberty in various spheres—religious, personal, political, and thesis, economic—proved more successful than we find in modern times. Thus if we want to know how to persuade people to accept the ideas of liberty and establish a free society, we should begin by reading our successful ancestors. Their ideas are as fresh and suggestive as the thesis statements issues day they were written, however old and dusty the books may be in how to which those ideas appear. Philosophy, unlike science, does not tend to advance through the progressive accumulation of knowledge.
The modern student of physics does not need to read Isaac Newton in order to learn about physics. Thesis For Controversial Issues? The student, if he reads Newton at all, does so because he is interested in thesis rights the origin of his science, not because he expects to find the best presentation of his subject matter. What remains of value in Newton has been sifted and refined by many generations of scientists, and the student can benefit from this cumulative process by reading a modern up-to-date text on statements physics. But philosophical theories, including ideas about essays critiquing liberty, do not follow this cumulative pattern. Rather, they tend to zig forward and statements for controversial, zag backward in an erratic and unpredictable fashion. The theory of liberty began to write zig noticeably in the seventeenth century. This trend continued, more or less, until the twentieth century brought us statism, collectivism, and total war. This highly retrogressive zag, which is probably the thesis issues most severe setback that liberty has ever suffered, continued virtually unchecked until the rebirth of libertarian theory a few decades ago.
Let me try to clarify the historical status of the modern movement through an analogy. The Italian Renaissance of the scholarship application without fifteenth century, which was an enthusiastic revival of Greek philosophy, science, and literature, paved the way for the Scientific Revolution. The European mind was stimulated to move forward by looking backward at the finest intellectual culture ever produced in thesis statements for controversial the Western World, that of ancient Greece. As libertarians we look forward to a revolution in liberty, but this lies somewhere in essay for class the future. Thesis Statements For Controversial Issues? We are currently in our renaissance stage, attempting to restore the lost or forgotten ideas of our predecessors.
The intellectual culture of the seventeenth and eighteenth centuries, a period rich in libertarian ideas, is to our renaissance what the on child culture of ancient Greece was to the Italian Renaissance—the source of our inspiration and statements, the foundation of our future progress. I suggest that libertarians can best move forward by first looking backward and of christmas, rediscovering the intellectual gems that were bequeathed to us by our libertarian progenitors, who were more advanced than we are, theoretically speaking, in several major areas. George H. Smith was formerly Senior Research Fellow for the Institute for Humane Studies, a lecturer on American History for thesis statements, Cato Summer Seminars, and Executive Editor of Knowledge Products. Smith's fourth book, The System of Liberty , was recently published by Cambridge University Press. Explore our growing library of content Start Exploring.
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