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{{pp-semi-indef|small=yes}} | |||
{{Short description|Object-oriented programming language}} | |||
{{Distinguish|Java (software platform)|JavaScript|Java|Javanese language}} | |||
{{Redirect|Openframe|the ten-pin bowling term|Open frame}} | |||
{{Use mdy dates|date=August 2017}} | |||
{{Infobox programming language | {{Infobox programming language | ||
|name = Java | | name = Java | ||
|logo = |
| logo = Java programming language logo.svg | ||
| logo size = 121px | |||
|paradigm = ] | |||
| logo caption = | |||
|year = 1990s | |||
| paradigm = ]: ], ] (]), ], ], ], ] | |||
|designer = ] | |||
| year = {{Start date and age|1995|5|23}}<ref>{{cite magazine|url=https://www.forbes.com/sites/oracle/2015/05/20/javas-20-years-of-innovation/|title=Java's 20 Years of Innovation|magazine=Forbes|date=May 20, 2015|access-date=March 18, 2016|author=Binstock, Andrew|archive-url=https://web.archive.org/web/20160314102242/http://www.forbes.com/sites/oracle/2015/05/20/javas-20-years-of-innovation/|archive-date=March 14, 2016|url-status=live}}</ref> | |||
|typing = strong, static | |||
| discontinued = <!-- Set to yes if software is discontinued, otherwise omit. --> | |||
|implementations = numerous | |||
| ver layout = <!-- simple (default) or stacked --> | |||
|dialects = | |||
| latest release version = {{wikidata|property|edit|reference|P548=Q2804309|P348}} | |||
|influenced_by = ], ] | |||
| latest release date = {{start date and age|{{wikidata|qualifier|single|P548=Q2804309|P348|P577}}}} | |||
|influenced = ] | |||
| designer = ] | |||
}}'''Java''' is an ] ] developed by ] and colleagues at ] in the early 1990s. The language, which was designed to be ], is a derivative of ] with a simpler ], a more robust ] and simplified ]. | |||
| developer = ] | |||
| typing = ], ], ] | |||
| memory management = ] | |||
| influenced_by = ],<ref name="BarbaraLiskov">{{cite book |title=Program Development in Java – Abstraction, Specification, and Object-Oriented Design|author=] with ]|isbn=978-0-201-65768-5|publisher=USA, Addison Wesley|year=2000}}</ref> ],<ref name="BarbaraLiskov" /> ],<ref name="BarbaraLiskov" /> ],<ref name="BarbaraLiskov" /> ], ],<ref>{{cite web|url=https://books.google.com/books?id=0rUtBAAAQBAJ&pg=PAPA133|title=Cracking The Java Programming Interview :: 2000+ Java Interview Que/Ans|first=Harry H.|last=Chaudhary|access-date=2016-05-29|date=2014-07-28|archive-date=September 29, 2023|archive-url=https://web.archive.org/web/20230929040943/https://books.google.com/books?id=0rUtBAAAQBAJ&pg=PAPA133#v=onepage&q&f=false|url-status=live}}</ref> ],<ref>Java 5.0 added several new language features (the ], ], ] and ]), after they were introduced in the similar (and competing) ] language. {{Webarchive|url=https://web.archive.org/web/20110319065438/http://www.barrycornelius.com/papers/java5/|date=March 19, 2011}} {{Webarchive|url=https://web.archive.org/web/20060107162045/http://www.levenez.com/lang/|date=January 7, 2006}}</ref> ],<ref>{{cite web|author1=Gosling, James|author2=McGilton, Henry|title=The Java Language Environment|date=May 1996|url=https://www.oracle.com/technetwork/java/langenv-140151.html|access-date=May 6, 2014|archive-url=https://web.archive.org/web/20140506214653/http://www.oracle.com/technetwork/java/langenv-140151.html|archive-date=May 6, 2014 |url-status=live}}</ref> ],<ref>{{cite web|author1=Gosling, James|author2=Joy, Bill |author3=Steele, Guy|author4=Bracha, Gilad|title=The Java Language Specification, 2nd Edition |url=https://java.sun.com/docs/books/jls/second_edition/html/intro.doc.html#237601|access-date=February 8, 2008|archive-url=https://web.archive.org/web/20110805051057/http://java.sun.com/docs/books/jls/second_edition/html/intro.doc.html#237601|archive-date=August 5, 2011 |url-status=live}}</ref> ],<ref>{{cite web |url=http://www.computerworld.com.au/index.php/id;1422447371;pp;3;fp;4194304;fpid;1|title=The A-Z of Programming Languages: Modula-3 |publisher=Computerworld|access-date=2010-06-09|url-status=dead|archive-url=https://web.archive.org/web/20090105145818/http://www.computerworld.com.au/index.php/id%3B1422447371%3Bpp%3B3%3Bfp%3B4194304%3Bfpid%3B1|archive-date=January 5, 2009}}</ref> ],<ref>] stated on a number of public occasions, e.g. in a lecture at the Polytechnic Museum, Moscow in September 2005 (several independent first-hand accounts in Russian exist, e.g. one with an audio recording: {{cite web|author=Filippova, Elena|title=Niklaus Wirth's lecture at the Polytechnic Museum in Moscow|date=September 22, 2005|url=http://www.delphikingdom.com/asp/viewitem.asp?catalogid=1155|access-date=November 20, 2011|archive-date=December 1, 2020|archive-url=https://web.archive.org/web/20201201054813/http://www.delphikingdom.com/asp/viewitem.asp?catalogid=1155|url-status=live}}), that the Sun Java design team licensed the Oberon compiler sources a number of years prior to the release of Java and examined it: a (relative) compactness, type safety, garbage collection, no multiple inheritance for classes{{snd}} all these key overall design features are shared by Java and Oberon.</ref> ],<ref>] cites ] as a strong influence on the design of the Java programming language, stating that notable direct derivatives include Java interfaces (derived from Objective-C's ]) and primitive wrapper classes. {{Webarchive|url=https://web.archive.org/web/20110713014816/http://cs.gmu.edu/~sean/stuff/java-objc.html|date=July 13, 2011}}</ref> ],<ref>{{cite web |url=http://www.fscript.org/prof/javapassport.pdf |quote=The project went ahead under the name ''green'' and the language was based on an old model of ], which makes it possible to generate interpretive code. |title=History of Java|work=Java Application Servers Report|author=TechMetrix Research|year=1999|archive-url=https://web.archive.org/web/20101229090912/http://www.fscript.org/prof/javapassport.pdf|archive-date=December 29, 2010|url-status=dead}}</ref><ref>{{cite web |title=A Conversation with James Gosling – ACM Queue |date=August 31, 2004 |url=http://queue.acm.org/detail.cfm?id=1017013 |publisher=Queue.acm.org |access-date=2010-06-09|archive-url=https://web.archive.org/web/20150716194245/http://queue.acm.org/detail.cfm?id=1017013|archive-date=July 16, 2015 |url-status=live}}</ref> ]<ref>{{cite report |author=((The Java Language Team)) |publisher=JavaSoft, Sun Microsystems, Inc. |url=http://java.sun.com/docs/white/delegates.html |quote=In the summer of 1996, Sun was designing the precursor to what is now the event model of the AWT and the JavaBeans component architecture. Borland contributed greatly to this process. We looked very carefully at Delphi Object Pascal and built a working prototype of bound method references in order to understand their interaction with the Java programming language and its APIs. |archive-url=https://web.archive.org/web/20120627043929/http://java.sun.com/docs/white/delegates.html |archive-date=2012-06-27 |url-status=dead |type=White Paper |title=About Microsoft's "Delegates"}}</ref> | |||
| influenced = ], ], ], ],<ref name="chplspec">{{cite web|title=Chapel spec (Acknowledgements)|url=http://chapel.cray.com/spec/spec-0.98.pdf|date=2015-10-01|access-date=2016-01-14|publisher=Cray Inc.|archive-url=https://web.archive.org/web/20160205114946/http://chapel.cray.com/spec/spec-0.98.pdf|archive-date=February 5, 2016|url-status=live}}</ref> ], ], ], ],<ref name="gambas">{{cite web|url=http://gambaswiki.org/doc/intro?nh&l=en|title=Gambas Documentation Introduction|publisher=Gambas Website|access-date=2017-10-09|archive-url=https://web.archive.org/web/20171009041815/http://gambaswiki.org/doc/intro?nh&l=en|archive-date=October 9, 2017|url-status=live}}</ref> ], ],<ref>{{cite magazine|url=http://www.infoworld.com/article/2610885/facebook-q-a--hack-brings-static-typing-to-php-world.html|title=Facebook Q&A: Hack brings static typing to PHP world|magazine=InfoWorld|date=March 26, 2014|access-date=2015-01-11|archive-url=https://web.archive.org/web/20150213220946/http://www.infoworld.com/article/2610885/facebook-q-a--hack-brings-static-typing-to-php-world.html|archive-date=February 13, 2015|url-status=live}}</ref> ], ], ], ], ], ], ], ], ], ], ] | |||
| website = {{ubl|{{URL|oracle.com/java/}}|{{URL|java.com}}|{{URL|dev.java}}}} | |||
| file_ext = .java, ], ], .jmod, ] | |||
| wikibooks = Java Programming | |||
}} | |||
'''Java''' is a ], ], ] ] that is designed to have as few implementation ] as possible. It is a ] programming language intended to let ]s ''write once, run anywhere'' (]),<ref>{{cite web|title=Write once, run anywhere?|date=May 2, 2002 |publisher=] |url=http://www.computerweekly.com/Articles/2002/05/02/186793/write-once-run-anywhere.htm|access-date=2009-07-27|url-status=live|archive-date=August 13, 2021|archive-url=https://web.archive.org/web/20210813193857/https://www.computerweekly.com/feature/Write-once-run-anywhere}}</ref> meaning that ] Java code can run on all platforms that support Java without the need to recompile.<ref name="design_goals">{{cite web |title=1.2 Design Goals of the Java Programming Language|date=January 1, 1999 |url=https://www.oracle.com/technetwork/java/intro-141325.html|access-date=2013-01-14|publisher=Oracle|archive-url=https://web.archive.org/web/20130123204103/http://www.oracle.com/technetwork/java/intro-141325.html|archive-date=January 23, 2013|url-status=live}}</ref> Java applications are typically compiled to ] that can run on any ] (JVM) regardless of the underlying ]. The ] of Java is similar to ] and ], but has fewer ] facilities than either of them. The Java runtime provides dynamic capabilities (such as ] and runtime code modification) that are typically not available in traditional compiled languages. | |||
Java is not related to ], though they have similar names and share a ]-like syntax. | |||
Java gained popularity shortly after its release, and has been a popular programming language since then.<ref>{{Cite web |last=Melanson |first=Mike |date=August 9, 2022 |title=Don't call it a comeback: Why Java is still champ |url=https://github.com/readme/featured/java-programming-language |url-status=live |archive-url=https://web.archive.org/web/20230825195416/https://github.com/readme/featured/java-programming-language |archive-date=August 25, 2023 |access-date=October 15, 2023 |website=]}}</ref> Java was the third most popular programming language in {{As of|2022|bare=yes}} according to ].<ref>{{Cite web |title=The top programming languages |url=https://octoverse.github.com/2022/top-programming-languages |url-status=live |archive-url=https://web.archive.org/web/20230802203718/https://octoverse.github.com/2022/top-programming-languages |archive-date=2 August 2023 |access-date=15 October 2023 |website=The State of the Octoverse |publisher=]}}</ref> Although still widely popular, there has been a gradual decline in use of Java in recent years with ] gaining popularity.<ref name=":0">{{cite magazine |last=McMillan |first=Robert |date=August 1, 2013 |title=Is Java Losing Its Mojo? |url=https://www.wired.com/2013/01/java-no-longer-a-favorite/ |url-access=limited |url-status=live |magazine=] |archive-url=https://web.archive.org/web/20170215115409/https://www.wired.com/2013/01/java-no-longer-a-favorite/ |archive-date=February 15, 2017 |access-date=October 15, 2023 |quote=}}</ref> | |||
==History== | |||
Java was designed by ] at ]. It was released in May 1995 as a core component of Sun's ]. The original and ] Java ]s, virtual machines, and ] were released by Sun under ]s. As of May 2007, in compliance with the specifications of the ], Sun had ] most of its Java technologies under the ] license. ], which bought Sun in 2010, offers its own ] Java Virtual Machine. However, the official ] is the ] JVM, which is open-source software used by most developers and is the default JVM for almost all Linux distributions. | |||
===Early history=== | |||
] | |||
The ] and language began as an internal project at ] in December of 1990. Engineer ] had become increasingly frustrated with the state of Sun's C++ and ] ]s (application programming interfaces) and tools. While considering moving to ], Naughton was offered a chance to work on new technology and thus the '''Stealth Project''' was started. | |||
] is the version current {{as of|lc=y|2024|September}}. Java 20 and 22 are no longer maintained. Java 8, 11, 17, and 21 are ] versions still under maintenance. | |||
The Stealth Project was soon renamed to the '''Green Project''' with ] and Mike Sheridan joining Naughton. Together with other engineers, they began work in a small office on ] in ]. They were attempting to develop a new technology for programming next generation smart appliances, which Sun expected to be a major new opportunity. | |||
== History == | |||
The team originally considered using C++, but it was rejected for several reasons. Because they were developing an ] with limited resources, they decided that C++ demanded too large a footprint and that its complexity led to developer errors. The language's lack of ] meant that programmers had to manually manage system memory, a challenging and error-prone task. The team was also troubled by the language's lack of portable facilities for security, ], and ]ing. Finally, they wanted a platform that could be easily ported to all types of devices. | |||
{{See also|Java (software platform)#History}} | |||
] | |||
], the creator of Java, in 2008]] | |||
], Mike Sheridan, and ] initiated the Java language project in June 1991.<ref>{{cite web |title=Java technology: The early years |last=Byous |first=Jon |date=c. 1998 |work=Sun Developer Network |publisher=] |url=https://java.sun.com/features/1998/05/birthday.html |access-date=2005-04-22 |url-status=dead |archive-url=https://web.archive.org/web/20050420081440/http://java.sun.com/features/1998/05/birthday.html |archive-date=April 20, 2005}}</ref> Java was originally designed for interactive television, but it was too advanced for the digital cable television industry at the time.<ref>Object-oriented programming {{cite web |title=The History of Java Technology |date=c. 1995 |work=Sun Developer Network |url=http://www.java.com/en/javahistory/ |access-date=2010-04-30 |url-status=dead |archive-url=https://web.archive.org/web/20100210225651/http://www.java.com/en/javahistory/ |archive-date=February 10, 2010}}</ref> The language was initially called '']'' after an ] tree that stood outside Gosling's office. Later the project went by the name ''Green'' and was finally renamed ''Java'', from ], a type of coffee from ].<ref>{{cite web |last1=Murphy |first1=Kieron |date=1996-10-04 |url=https://www.infoworld.com/article/2077265/so-why-did-they-decide-to-call-it-java-.html |title=So why did they decide to call it Java? |work=] |access-date=2020-07-13 |archive-date=July 13, 2020 |archive-url=https://web.archive.org/web/20200713234202/https://www.infoworld.com/article/2077265/so-why-did-they-decide-to-call-it-java-.html |url-status=live}}</ref> Gosling designed Java with a ]/]-style syntax that system and application programmers would find familiar.<ref>Kabutz, Heinz; {{Webarchive|url=https://web.archive.org/web/20070413072630/http://www.artima.com/weblogs/viewpost.jsp?thread=7555 |date=April 13, 2007}}. Artima. Retrieved April 29, 2007.</ref> | |||
] had envisioned a new language combining the best of ] and C. In a paper called ''Further'', he proposed to Sun that its engineers should produce an ] environment based on C++. Initially, Gosling attempted to modify and extend C++, which he referred to as C++ ++ -- , but soon abandoned that in favor of creating an entirely new language, which he called '''Oak''' after the tree that stood just outside his office. | |||
Sun Microsystems released the first public implementation as Java 1.0 in 1996.<ref name="oraclejavahistory">{{cite web |url=http://www.sun.com/smi/Press/sunflash/1996-01/sunflash.960123.10561.xml |archive-url=https://web.archive.org/web/20070310235103/http://www.sun.com/smi/Press/sunflash/1996-01/sunflash.960123.10561.xml |url-status=dead |archive-date=2007-03-10 |title=JAVASOFT SHIPS JAVA 1.0 |access-date=2018-05-13}}</ref> It promised ] (WORA) functionality, providing no-cost run-times on popular ]. Fairly secure and featuring configurable security, it allowed network- and file-access restrictions. Major ]s soon incorporated the ability to run ]s within web pages, and Java quickly became popular. The Java 1.0 compiler was re-written ] by ] to comply strictly with the Java 1.0 language specification.<ref>{{cite book |url={{Google books|rXGMFYXFDwMC|plainurl=yes}} |title=Object-oriented Programming with Java: Essentials and Applications |publisher=Tata McGraw-Hill Education |page=34}}</ref> With the advent of Java 2 (released initially as J2SE 1.2 in December 1998{{snd}} 1999), new versions had multiple configurations built for different types of platforms. ] included technologies and APIs for enterprise applications typically run in server environments, while J2ME featured APIs optimized for mobile applications. The desktop version was renamed J2SE. In 2006, for marketing purposes, Sun renamed new J2 versions as '']'', '']'', and '']'', respectively. | |||
The team worked long hours and by the summer of 1992, they were able to demonstrate portions of the new platform including the Green ], the Oak language, the libraries, and the hardware. Their first attempt, demonstrated on ], ], focused on building a ] device named '''Star7'''{{ref|star7}} which had a graphical interface and a smart agent called "Duke" to assist the user. In November of that year, the Green Project was spun off to become '''FirstPerson, Inc''', a wholly owned subsidiary of Sun Microsystems, and the team relocated to Palo Alto. The FirstPerson team was interested in building highly interactive devices, and when ] issued an ] for a ], FirstPerson changed their target and responded with a proposal for a set-top box platform. However, the ] industry felt that their platform gave too much control to the user and FirstPerson lost their bid to ]. An additional deal with ] for a set-top box also failed to materialize. Unable to generate interest within the TV industry, the company was rolled back into Sun. | |||
In 1997, Sun Microsystems approached the ] standards body and later the ] to formalize Java, but it soon withdrew from the process.<ref>{{cite web|url=http://www.open-std.org/JTC1/SC22/JSG/|title=JSG – Java Study Group|work=open-std.org|access-date=August 2, 2006|archive-url=https://web.archive.org/web/20060825082008/http://www.open-std.org/JTC1/SC22/JSG/|archive-date=August 25, 2006|url-status=live}}</ref><ref>{{cite web |title=Why Java Was – Not – Standardized Twice |url=http://www.computer.org/csdl/proceedings/hicss/2001/0981/05/09815015.pdf |access-date=June 3, 2018 |archive-url=https://web.archive.org/web/20140113101235/http://www.computer.org/csdl/proceedings/hicss/2001/0981/05/09815015.pdf |archive-date=January 13, 2014 |url-status=live}}</ref><ref>{{cite web |url=http://www.zdnet.com/news/what-is-ecma-and-why-microsoft-cares/298821 |title=What is ECMA—and why Microsoft cares |website=] |access-date=May 6, 2014 |archive-url=https://web.archive.org/web/20140506215226/http://www.zdnet.com/news/what-is-ecma-and-why-microsoft-cares/298821 |archive-date=May 6, 2014 |url-status=live}}</ref> Java remains a ], controlled through the ].<ref>{{cite web |url=http://www.jcp.org/en/home/index |title=Java Community Process website |publisher=Jcp.org |date=May 24, 2010 |access-date=2010-06-09 |archive-url=https://web.archive.org/web/20060808070528/http://www.jcp.org/en/home/index |archive-date=August 8, 2006 |url-status=live}}</ref> At one time, Sun made most of its Java implementations available without charge, despite their ] status. Sun generated revenue from Java through the selling of licenses for specialized products such as the Java Enterprise System. | |||
===Java meets the Internet=== | |||
In June and July of 1994, after a three-day brainstorming session with ], ], Joy, Naughton, ], and ], the team re-targeted the platform for the ]. They felt that with the advent of the ] browser, the Internet was on its way to evolving into the same highly interactive medium that they had envisioned for cable TV. As a prototype, Naughton wrote a small web browser, WebRunner, later renamed ]. | |||
On November 13, 2006, Sun released much of its Java virtual machine (JVM) as ] (FOSS), under the terms of the ] license. On May 8, 2007, Sun finished the process, making all of its JVM's core code available under ]/open-source distribution terms, aside from a small portion of code to which Sun did not hold the copyright.<ref>{{cite web |url=http://grnlight.net/index.php/programming-articles/115-javaone-sun-the-bulk-of-java-is-open-sourced |title=JAVAONE: Sun – The bulk of Java is open sourced |publisher=GrnLight.net |access-date=2014-05-26 |archive-url=https://web.archive.org/web/20140527220942/http://grnlight.net/index.php/programming-articles/115-javaone-sun-the-bulk-of-java-is-open-sourced |archive-date=May 27, 2014 |url-status=live}}</ref> | |||
That year, the language was renamed '''Java''' after a ] search revealed that the name "Oak" was used by a manufacturer of video adaptor cards. The name Java was coined at a local coffee shop frequented by some of the members. It is not clear whether the name is an acronym or not; although some accounts claim that it stands for the names of '''J'''ames Gosling, '''A'''rthur '''V'''an Hoff, and '''A'''ndy Bechtolsheim, or '''J'''ust '''A'''nother '''V'''ague '''A'''cronym, it is generally accepted that "Java" does not stand for anything. Lending credence to the idea that Java owes its name to the products sold at the coffee shop is the fact that the first 4 bytes (the so-called "]") of any ] are, in ], 0xCAFEBABE. | |||
Sun's vice-president Rich Green said that Sun's ideal role with regard to Java was as an ''evangelist''.<ref>{{cite web|url=http://onjava.com/pub/a/onjava/2002/04/17/evangelism.html|title=Sun's Evolving Role as Java Evangelist|publisher=]|archive-url=https://web.archive.org/web/20100915162748/http://onjava.com/pub/a/onjava/2002/04/17/evangelism.html|archive-date=September 15, 2010|url-status=live|access-date=August 2, 2009 | |||
In October of 1994, ] and the Java platform was demonstrated for Sun executives. Java 1.0a was made available for download in 1994, but the first public release of Java and the HotJava ] came on ], ], at the ] conference. The announcement was made by ], the Director of Science for Sun Microsystems. His announcement was accompanied by a surprise announcement by ], Executive Vice President of ], that Netscape would be including Java support in its browsers. On ], ], the ] business group was formed by Sun Microsystems to develop the technology. Two weeks later the first version of Java was released. | |||
}}</ref> Following ]'s acquisition of Sun Microsystems in 2009–10, Oracle has described itself as the steward of Java technology with a relentless commitment to fostering a community of participation and transparency.<ref>{{cite web |url=https://www.oracle.com/us/technologies/java/|title=Oracle and Java|work=oracle.com|publisher=Oracle Corporation |access-date=2010-08-23|quote=Oracle has been a leading and substantive supporter of Java since its emergence in 1995 and takes on the new role as steward of Java technology with a relentless commitment to fostering a community of participation and transparency. |url-status=dead|archive-url=https://web.archive.org/web/20100131091008/http://www.oracle.com/us/technologies/java/ |archive-date=January 31, 2010}}</ref> This did not prevent Oracle from filing a lawsuit against Google shortly after that for using Java inside the ] (see the '']'' section). | |||
On April 2, 2010, James Gosling resigned from ].<ref>{{cite web|url=http://nighthacks.com/roller/jag/entry/time_to_move_on |title=Time to move on... |last=Gosling |first=James |date=April 9, 2010 |work=On a New Road |access-date=2011-11-16 |author-link=James Gosling |url-status=dead |archive-url=https://web.archive.org/web/20101105031239/http://nighthacks.com/roller/jag/entry/time_to_move_on |archive-date=November 5, 2010}}</ref> | |||
===Recent history=== | |||
After several years of popularity, Java's place in the browser has steadily eroded. For simple interactive animations, it has been almost completely superseded by ] and ]. ] its use is mostly limited to more complex applications like ]. It has also suffered from a lack of support by ] which no longer includes the Java platform with ] or ]. | |||
In January 2016, Oracle announced that Java run-time environments based on JDK 9 will discontinue the browser plugin.<ref>{{cite web|url=https://blogs.oracle.com/java-platform-group/entry/moving_to_a_plugin_free|title=Moving to a Plugin-Free Web|first=Dalibor|last=Topic|access-date=March 15, 2016|archive-url=https://web.archive.org/web/20160316164325/https://blogs.oracle.com/java-platform-group/entry/moving_to_a_plugin_free|archive-date=March 16, 2016|url-status=live}}</ref> | |||
By contrast, on the server side of the Web, Java is far more popular than ever, with many websites using ] and other Java-based technologies. | |||
Java software runs on everything from laptops to ]s, ] to scientific ]s.<ref>{{cite web|title=Learn About Java Technology|url=http://www.java.com/en/about/|publisher=Oracle|access-date=November 21, 2011|archive-url=https://web.archive.org/web/20111124090716/http://www.java.com/en/about/|archive-date=November 24, 2011|url-status=live}}</ref> | |||
On the desktop, stand-alone Java applications remain relatively rare because of their large ]. However, with the great advances in computer power in the last decade along with improvements in VM and compiler quality, several have gained widespread use, including the ] and ] ]s, and file sharing clients such as ] and ]. Java is also used in the ] mathematics program for rendering the ] and for part of the calculation functionality. Java Swing desktop applications are being developed as an alternative to ] technology. | |||
] (and others) highly recommend uninstalling outdated and unsupported versions of Java, due to unresolved security issues in older versions.<ref>{{Cite web|url=https://www.java.com/en/download/faq/remove_olderversions.xml|title=Why should I uninstall older versions of Java from my system?|publisher=Oracle|access-date=2021-09-24|archive-date=February 12, 2018|archive-url=https://web.archive.org/web/20180212011608/https://java.com/en/download/faq/remove_olderversions.xml|url-status=live}}</ref> | |||
===Version history=== | |||
], first introduced for '''J2SE 1.3''', allows provisioning applications over the ] by clicking a ] or a link on a website.]] | |||
The Java language has undergone several changes since JDK (]) 1.0 as well as numerous additions of classes and packages to the standard ]. Since J2SE 1.4, the evolution of the Java Language has been governed by the ] (JCP), which uses ''Java Specification Requests'' (JSRs) to proposed and specify additions and changes to the Java platform. The language is specified by the ''Java Language Specification'' (JLS); changes to the JLS are managed under . | |||
=== Principles === | |||
* '''JDK 1.0''' (], ]) — Initial release. ] | |||
There were five primary goals in creating the Java language:<ref name="design_goals" /> | |||
<!-- these are quoted directly from the source, please do not remove or change any of them! --> | |||
# It must be simple, ], and familiar. | |||
# It must be ] and secure. | |||
# It must be architecture-neutral and portable. | |||
# It must execute with high performance. | |||
# It must be ], ], and ]. | |||
=== Versions === | |||
* '''JDK 1.1''' (], ]) — Major additions included: ] | |||
{{Main|Java version history}} | |||
** an extensive retooling of the ] event model | |||
{{As of|2024|11}}, Java 8, 11, 17, and 21 are supported as ] (LTS) versions, with Java 25, releasing in September 2025, as the next scheduled LTS version.<ref>{{cite web |title=Oracle Java SE Support Roadmap |publisher=Oracle |date=September 13, 2021 |url=https://www.oracle.com/java/technologies/java-se-support-roadmap.html|access-date=September 18, 2021|archive-url=https://web.archive.org/web/20210919090451/https://www.oracle.com/java/technologies/java-se-support-roadmap.html |archive-date=2021-09-19|url-status=live}}</ref> | |||
** ]es added to the language | |||
** ] | |||
** ] | |||
** ] | |||
Oracle released the last zero-cost public update for the ] version ] LTS in January 2019 for commercial use, although it will otherwise still support Java 8 with public updates for personal use indefinitely. Other vendors such as ] continue to offer free builds of OpenJDK's long-term support (LTS) versions. These builds may include additional security patches and bug fixes.<ref>{{cite web |title=Temurin™ Support; Adoptium |url=https://adoptium.net/support/ |website=adoptium.net |access-date=29 March 2024 |archive-url=https://web.archive.org/web/20240329061257/https://adoptium.net/support/ |archive-date=29 March 2024 |url-status=live}}</ref> | |||
* '''J2SE 1.2''' (], ]) — Codename ''Playground''. This and subsequent releases through J2SE 5.0 were rebranded '''Java 2''' and the version name "J2SE" (]) replaced JDK to distinguish the base platform from J2EE (]) and J2ME (]). Major additions included: ] | |||
** <code>]</code> keyword | |||
** ] | |||
** the ] graphical API was integrated into the core classes | |||
** Sun's JVM was equipped with a ] for the first time | |||
** ] | |||
** ], an ] implementation for ] interoperability | |||
** ] framework | |||
Major release versions of Java, along with their release dates: | |||
* '''J2SE 1.3''' (], ]) — Codename ''Kestrel''. The most notable changes were:] ] | |||
** ] JVM included (the HotSpot JVM was first released in April, 1999 for the J2SE 1.2 JVM) | |||
** ] was changed to be based on ] | |||
** ] | |||
** ] (JNDI) included in core libraries (previously available as an extension) | |||
** ] (JPDA) | |||
{| class="wikitable" | |||
* '''J2SE 1.4''' (], ]) — Codename ''Merlin''. This was the first release of the Java platform developed under the Java Community Process as . Major changes included: ]] | |||
! Version !! Date | |||
** <code>]</code> keyword (Specified in .) | |||
|- | |||
** ] modeled after ] regular expressions | |||
| JDK ] || 1995 | |||
** ] allows an exception to encapsulate original lower-level exception | |||
|- | |||
** non-blocking NIO (]) (Specified in .) | |||
| JDK 1.0 || January 23, 1996<ref>{{cite web|url=http://www.sun.com/smi/Press/sunflash/1996-01/sunflash.960123.10561.xml |title=JAVASOFT SHIPS JAVA 1.0|website=sun.com |access-date=2008-02-05 |url-status=dead |archive-url=https://web.archive.org/web/20070310235103/http://www.sun.com/smi/Press/sunflash/1996-01/sunflash.960123.10561.xml |archive-date=March 10, 2007}}</ref> | |||
** logging API (Specified in .) | |||
|- | |||
** image I/O API for reading and writing images in formats like ] and ] | |||
| JDK 1.1 || February 19, 1997 | |||
** integrated ] parser and ] processor (]) (Specified in and .) | |||
|- | |||
** integrated security and cryptography extensions (JCE, ], ]) | |||
| J2SE 1.2 || December 8, 1998 | |||
** ] included (Java Web Start was first released in March, 2001 for J2SE 1.3) (Specified in .) | |||
|- | |||
| J2SE 1.3 || May 8, 2000 | |||
* '''J2SE 5.0''' (], ]) — Codename ''Tiger''. (Originally numbered 1.5, which is still used as the internal version number.) Developed under , Tiger added a number of significant new language features: ] | |||
|- | |||
** ] — provides compile-time (static) ] for collections and eliminates the need for most ]. (Specified by .) | |||
| J2SE 1.4 || February 6, 2002 | |||
** ] — also called ]s, allows language constructs such as classes and methods to be tagged with additional data, which can then be processed by metadata-aware utilities. (Specified by .) | |||
|- | |||
** ]/unboxing — automatic conversions between ]s (such as <code>int</code>) and ]es (such as {{Javadoc:SE|java/lang|Integer}}). (Specified by .) | |||
| J2SE 5.0 || September 30, 2004 | |||
** ] — the <code>enum</code> keyword creates a ], ordered list of values (such as <code>Day.MONDAY</code>, <code>Day.TUESDAY</code>, etc.). Previously this could only be achieved by non-typesafe constant integers or manually constructed classes (typesafe enum pattern). (Specified by JSR 201.) | |||
|- | |||
** Enhanced <code>for</code> ]—the <code>for</code> loop syntax is extended with special syntax for iterating over each member of any {{Javadoc:SE|java/lang|Iterable}}, such as an array or {{Javadoc:SE|java/util|Collection}}, using a construct of the form: | |||
| Java SE 6 || December 11, 2006 | |||
|- | |||
<!-- The table below indents the code example and following text by 32 pixels --> | |||
| Java SE 7 || July 28, 2011 | |||
{| | |||
|- | |||
| style="width:32px" | | |||
| Java SE 8 (LTS) || March 18, 2014 | |||
| | |||
|- | |||
void displayWidgets (Iterable<Widget> widgets) { | |||
| Java SE 9 || September 21, 2017 | |||
for (Widget w : widgets) { | |||
|- | |||
w.display(); | |||
| Java SE 10 || March 20, 2018 | |||
} | |||
|- | |||
} | |||
| Java SE 11 (LTS) || September 25, 2018<ref>{{cite news|url=https://blogs.oracle.com/java-platform-group/introducing-java-se-11|title=Introducing Java SE 11|first=Sharat|last=Chander|website=oracle.com|access-date=September 26, 2018|archive-url=https://web.archive.org/web/20180926093144/https://blogs.oracle.com/java-platform-group/introducing-java-se-11|archive-date=September 26, 2018|url-status=live}}</ref> | |||
This example iterates over the <code>Iterable</code> object <code>widgets</code>, assigning each of its items in turn to the variable <code>w</code>, and then calling the <code>Widget</code> method <code>display()</code> for each item. (Specified by JSR 201.) | |||
|- | |||
| Java SE 12 || March 19, 2019 | |||
|- | |||
| Java SE 13 || September 17, 2019 | |||
|- | |||
| Java SE 14 || March 17, 2020 | |||
|- | |||
| Java SE 15 || September 15, 2020<ref>{{cite news|url=https://blogs.oracle.com/java-platform-group/the-arrival-of-java-15|title=The Arrival of Java 15!|date=September 15, 2020|publisher=]|access-date=2020-09-15|archive-date=September 16, 2020|archive-url=https://web.archive.org/web/20200916092332/https://blogs.oracle.com/java-platform-group/the-arrival-of-java-15|url-status=live |last1=Chander |first1=Sharat }}</ref> | |||
|- | |||
| Java SE 16 || March 16, 2021 | |||
|- | |||
| Java SE 17 (LTS) || September 14, 2021 | |||
|- | |||
| Java SE 18 || March 22, 2022 | |||
|- | |||
| Java SE 19 || September 20, 2022 | |||
|- | |||
| Java SE 20 || March 21, 2023 | |||
|- | |||
| Java SE 21 (LTS) || September 19, 2023<ref>{{Cite web|url=https://openjdk.org/projects/jdk/21/|title=JDK 21|website=openjdk.org|access-date=September 20, 2023|archive-date=September 20, 2023|archive-url=https://web.archive.org/web/20230920173515/https://openjdk.org/projects/jdk/21/|url-status=live}}</ref> | |||
|- | |||
| Java SE 22 || March 19, 2024 | |||
|- | |||
| Java SE 23 || September 17, 2024 | |||
|} | |} | ||
== Editions == | |||
* '''Java SE 6''' — Codename . ] this is currently in development under . A beta version was released on February 15, 2006 ] and is available at . Another beta is expected summer 2006 with the final release in autumn 2006. New builds including enhancements and bug fixes are released approximately weekly. As of this version, Sun replaced the name "J2SE" with '''Java SE''' and dropped the ".0" from the version number. | |||
{{See also|Free Java implementations#Class library}} | |||
{{Java platforms}} | |||
Sun has defined and supports four editions of Java targeting different application environments and segmented many of its ] so that they belong to one of the platforms. The platforms are: | |||
* ] for smart-cards.<ref name="java_card">{{cite web |url=https://www.oracle.com/technetwork/java/embedded/javacard/overview/ |title=Java Card Overview |publisher=Oracle |work=Oracle Technology Network |access-date=December 18, 2014 |archive-url=https://web.archive.org/web/20150107034738/http://www.oracle.com/technetwork/java/embedded/javacard/overview/ |archive-date=January 7, 2015 |url-status=live}}</ref> | |||
* ] (Java ME) – targeting environments with limited resources.<ref name="java_me">{{cite web |url=https://www.oracle.com/technetwork/java/embedded/javame/ |title=Java Platform, Micro Edition (Java ME) |publisher=Oracle |work=Oracle Technology Network |access-date=December 18, 2014 |archive-url=https://web.archive.org/web/20150104210546/http://www.oracle.com/technetwork/java/embedded/javame/ |archive-date=January 4, 2015 |url-status=live}}</ref> | |||
* ] (Java SE) – targeting workstation environments.<ref name="java_se">{{cite web |url=https://www.oracle.com/technetwork/java/javase/overview/ |title=Java SE |publisher=Oracle |work=Oracle Technology Network |access-date=December 18, 2014 |archive-url=https://web.archive.org/web/20141224184532/http://www.oracle.com/technetwork/java/javase/overview/ |archive-date=December 24, 2014 |url-status=live}}</ref> | |||
* ] (Java EE) – targeting large distributed enterprise or Internet environments.<ref name="java_ee">{{cite web |url=https://www.oracle.com/technetwork/java/javaee/overview/ |title=Java Platform, Enterprise Edition (Java EE) |publisher=Oracle |work=Oracle Technology Network |access-date=December 18, 2014 |archive-url=https://web.archive.org/web/20141217155326/http://www.oracle.com/technetwork/java/javaee/overview/ |archive-date=December 17, 2014 |url-status=live}}</ref> | |||
The ] in the Java APIs are organized into separate groups called ]. Each package contains a set of related ], classes, subpackages and ]. | |||
* '''Java SE 7''' — Codename <!--enable when some actual content becomes available: -->''Dolphin''. ], this is in the early planning stages. Development is expected to begin in spring 2006, with release estimated in 2008. | |||
Sun also provided an edition called ] that has been superseded by later, standards-based Java ME configuration-profile pairings. | |||
In addition to the language changes, much more dramatic changes have been made to the Java class library over the years, which has grown from a few hundred classes in JDK 1.0 to over three thousand in J2SE 5.0. Entire new APIs, such as ] and ], have been introduced, and many of the original JDK 1.0 classes and methods have been ]. | |||
== Execution system == | |||
==Philosophy== | |||
=== Java JVM and bytecode === | |||
{{Main|Java (software platform)|Java virtual machine}} | |||
<!-- we apparently have two main sections for what seems to be the same thing. Merge needed? --> | |||
One design goal of Java is ], which means that programs written for the Java platform must run similarly on any combination of hardware and operating system with adequate run time support. This is achieved by compiling the Java language code to an intermediate representation called ], instead of directly to architecture-specific ]. Java bytecode instructions are analogous to machine code, but they are intended to be executed by a ] (VM) written specifically for the host hardware. ] commonly use a ] (JRE) installed on their device for standalone Java applications or a web browser for ]s. | |||
There were five primary goals in the creation of the Java language: | |||
Standard libraries provide a generic way to access host-specific features such as graphics, ], and ]. | |||
#It should use the ] methodology. | |||
#It should allow the same program to be executed on multiple operating systems. | |||
#It should contain built-in support for using ]. | |||
#It should be designed to execute code from remote sources securely. | |||
#It should be easy to use and borrow the good parts of older object-oriented languages like C++. | |||
The use of universal bytecode makes porting simple. However, the overhead of ] bytecode into machine instructions made interpreted programs almost always run more slowly than native ]s. ] (JIT) compilers that compile byte-codes to machine code during runtime were introduced from an early stage. Java's Hotspot compiler is actually two compilers in one; and with ] (included in e.g. Java 11, but removed as of Java 16) allowing ].<ref>{{Cite web |date=2021-08-06 |title=Deep Dive Into the New Java JIT Compiler – Graal {{!}} Baeldung |url=https://www.baeldung.com/graal-java-jit-compiler |access-date=2021-10-13 |website=www.baeldung.com |language=en-US |archive-date=October 28, 2021 |archive-url=https://web.archive.org/web/20211028165746/https://www.baeldung.com/graal-java-jit-compiler |url-status=live }}</ref> Java itself is platform-independent and is adapted to the particular platform it is to run on by a ] (JVM), which translates the ] into the platform's machine language.<ref>{{cite web|url=http://www.programmerinterview.com/index.php/java-questions/jvm-platform-dependent/|title=Is the JVM (Java Virtual Machine) platform dependent or platform independent? What is the advantage of using the JVM, and having Java be a translated language?|publisher=Programmer Interview|access-date=2015-01-19|archive-url=https://web.archive.org/web/20150119144223/http://www.programmerinterview.com/index.php/java-questions/jvm-platform-dependent/ |archive-date=January 19, 2015|url-status=live}}</ref> | |||
Especially for the latter part, however, extensions are sometimes required, like ] or ]. | |||
=== |
==== Performance ==== | ||
{{Main|Java performance}} | |||
The first characteristic, ] ("OO"), refers to a method of programming and language design. | |||
Although there are many interpretations of OO, one primary distinguishing idea is to design software so that the various types of data it manipulates are combined together with their relevant operations. Thus, data and code are combined into entities called ]. An object can be thought of as a self-contained bundle of ''behavior'' (code) and ''state'' (data). The principle is to separate the things that change from the things that stay the same; often, a change to some data structure requires a corresponding change to the code that operates on that data, or vice versa. This separation into coherent objects provides a more stable foundation for a software system's design. The intent is to make large software projects easier to manage, thus improving quality and reducing the number of failed projects. | |||
Programs written in Java have a reputation for being slower and requiring more memory than those written in ].<ref name=Jelovic>{{cite web |title=Why Java will always be slower than C++ |last=Jelovic |first=Dejan |url=http://www.jelovic.com/articles/why_java_is_slow.htm |access-date=2008-02-15 |url-status=dead |archive-url=https://web.archive.org/web/20080211111923/http://www.jelovic.com/articles/why_java_is_slow.htm |archive-date=February 11, 2008}}</ref><ref>{{cite web |last=Hundt |first=Robert |title=Loop Recognition in C++/Java/Go/Scala |url=https://days2011.scala-lang.org/sites/days2011/files/ws3-1-Hundt.pdf |access-date=2012-07-12 |url-status=live |archive-url=https://web.archive.org/web/20111116151424/https://days2011.scala-lang.org/sites/days2011/files/ws3-1-Hundt.pdf |archive-date=November 16, 2011}}</ref> However, Java programs' execution speed improved significantly with the introduction of ] in 1997/1998 for ],<ref>{{cite web |url=http://www.symantec.com/about/news/release/article.jsp?prid=19970407_03 |title=Symantec's Just-In-Time Java Compiler To Be Integrated into Sun JDK 1.1 |access-date=August 1, 2009 |archive-url=https://web.archive.org/web/20100628171748/http://www.symantec.com/about/news/release/article.jsp?prid=19970407_03 |archive-date=June 28, 2010 |url-status=dead}}</ref> the addition of language features supporting better code analysis (such as inner classes, the StringBuilder class, optional assertions, etc.), and optimizations in the Java virtual machine, such as ] becoming Sun's default JVM in 2000. With Java 1.5, the performance was improved with the addition of the {{code|java.util.concurrent}} package, including ] implementations of the ] and other multi-core collections, and it was improved further with Java 1.6. | |||
Another primary goal of OO programming is to develop more generic objects so that software can become more reusable between projects. A generic "customer" object, for example, should in theory have roughly the same basic set of behaviors between different software projects, especially when these projects overlap on some fundamental level as they often do in large organizations. In this sense, software objects can hopefully be seen more as pluggable ], helping the software industry build projects largely from existing and well tested pieces, thus leading to a massive reduction in development times. Software reusability has met with mixed practical results, with two main difficulties: the design of truly generic objects is poorly-understood, and a methodology for broad communication of reuse opportunities is lacking. Some open source communities want to help ease the reuse problem, by providing authors with ways to disseminate information about generally reusable objects and object libraries. | |||
=== |
=== Non-JVM === | ||
Some platforms offer direct hardware support for Java; there are micro controllers that can run Java bytecode in hardware instead of a software Java virtual machine,<ref>{{Cite journal|last1=Salcic|first1=Zoran|last2=Park|first2=Heejong|last3=Teich|first3=Jürgen|last4=Malik|first4=Avinash|last5=Nadeem|first5=Muhammad|date=2017-07-22|title=Noc-HMP: A Heterogeneous Multicore Processor for Embedded Systems Designed in SystemJ|journal=ACM Transactions on Design Automation of Electronic Systems |volume=22|issue=4|pages=73|doi=10.1145/3073416|s2cid=11150290|issn=1084-4309}}</ref> and some ]-based processors could have hardware support for executing Java bytecode through their ] option, though support has mostly been dropped in current implementations of ARM. | |||
] of Java Swing ]s is independent of the platform on which they are running]] | |||
The second characteristic, ], means that ]s written in the Java language must run similarly on diverse hardware. One should be able to write a program once and run it anywhere. | |||
=== Automatic memory management === | |||
This is achieved by most Java ] by compiling the Java language code "halfway" to ] (specifically ]) —simplified machine instructions specific to the Java platform. The code is then run on a ] (VM), a program written in native code on the host hardware that ] and executes generic Java bytecode. Further, standardized libraries are provided to allow access to features of the host machines (such as graphics, ] and ]) in unified ways. Note that, although there's an explicit compiling stage, at some point, the Java bytecode is ] or converted to native ] by the ]. | |||
Java uses an ] to manage memory in the ]. The programmer determines when objects are created, and the Java runtime is responsible for recovering the memory once objects are no longer in use. Once no references to an object remain, the ] becomes eligible to be freed automatically by the garbage collector. Something similar to a ] may still occur if a programmer's code holds a reference to an object that is no longer needed, typically when objects that are no longer needed are stored in containers that are still in use.{{sfn|Bloch|2018|loc=§Item 7: Eliminate obsolete object references|p=26-28}} If methods for a non-existent object are called, a ] exception is thrown.<ref>{{cite web |url=http://docs.oracle.com/javase/8/docs/api/java/lang/NullPointerException.html |title=NullPointerException |publisher=Oracle |access-date=2014-05-06 |archive-url=https://web.archive.org/web/20140506214735/http://docs.oracle.com/javase/8/docs/api/java/lang/NullPointerException.html |archive-date=May 6, 2014 |url-status=live}}</ref><ref>{{cite web |url=http://www.artima.com/designtechniques/exceptions.html |title=Exceptions in Java |publisher=Artima.com |access-date=2010-08-10 |archive-url=https://web.archive.org/web/20090121152332/http://www.artima.com/designtechniques/exceptions.html |archive-date=January 21, 2009 |url-status=live}}</ref> | |||
One of the ideas behind Java's automatic memory management model is that programmers can be spared the burden of having to perform manual memory management. In some languages, memory for the creation of objects is implicitly allocated on the ] or explicitly allocated and deallocated from the ]. In the latter case, the responsibility of managing memory resides with the programmer. If the program does not deallocate an object, a ] occurs.{{sfn|Bloch|2018|loc=§Item 7: Eliminate obsolete object references|p=26-28}} If the program attempts to access or deallocate memory that has already been deallocated, the result is undefined and difficult to predict, and the program is likely to become unstable or crash. This can be partially remedied by the use of ]s, but these add overhead and complexity. Garbage collection does not prevent ] leaks, i.e. those where the memory is still referenced but never used.{{sfn|Bloch|2018|loc=§Item 7: Eliminate obsolete object references|p=26-28}} | |||
There are also implementations of Java compilers that compile to native ], such as ], removing the intermediate bytecode stage, but the output of these compilers can only be run on a single ]. | |||
Garbage collection may happen at any time. Ideally, it will occur when a program is idle. It is guaranteed to be triggered if there is insufficient free memory on the heap to allocate a new object; this can cause a program to stall momentarily. Explicit memory management is not possible in Java. | |||
Sun's license for Java insists that all implementations be "compatible". This resulted in a legal dispute with Microsoft after Sun claimed that the Microsoft implementation did not support the RMI and JNI interfaces and had added platform-specific features of their own. Sun sued and won both damages (some $20 million) and a court order enforcing the terms of the license from Sun. In response, Microsoft no longer ships Java with Windows, and in recent versions of Windows, Internet Explorer cannot support Java applets without a third-party plugin. However, Sun and others have made available Java run-time systems at no cost for those and other versions of Windows. | |||
Java does not support C/C++ style ], where object addresses can be arithmetically manipulated (e.g. by adding or subtracting an offset). This allows the garbage collector to relocate referenced objects and ensures type safety and security. | |||
The first implementations of the language used an interpreted virtual machine to achieve ]. These implementations produced programs that ran more slowly than programs written in C or C++, so the language suffered a reputation for poor performance. More recent JVM implementations produce programs that run significantly faster than before, using multiple techniques. | |||
As in C++ and some other object-oriented languages, variables of Java's ]s are either stored directly in fields (for objects) or on the ] (for methods) rather than on the heap, as is commonly true for non-primitive data types (but see ]). This was a conscious decision by Java's designers for performance reasons. | |||
The first technique is to simply compile directly into native code like a more traditional compiler, skipping bytecodes entirely. This achieves good performance, but at the expense of portability. Another technique, known as ''just-in-time compilation'' (JIT), translates the Java bytecodes into native code at the time that the program is run. More sophisticated VMs use '']'', in which the VM can analyze the behavior of the running program and selectively recompile and optimise critical parts of the program. Dynamic recompilation can achieve optimizations superior to static compilation because the dynamic compiler can base optimizations on knowledge about the runtime environment and the set of loaded classes. JIT compilation and dynamic recompilation allow Java programs to take advantage of the speed of native code without losing portability. | |||
Java contains multiple types of garbage collectors. Since Java 9, HotSpot uses the ] (G1GC) as the default.<ref>{{cite web |url=https://docs.oracle.com/javase/7/docs/technotes/guides/vm/performance-enhancements-7.html |title=Java HotSpot™ Virtual Machine Performance Enhancements |publisher=Oracle.com |access-date=2017-04-26 |archive-url=https://web.archive.org/web/20170529071720/http://docs.oracle.com/javase/7/docs/technotes/guides/vm/performance-enhancements-7.html |archive-date=May 29, 2017 |url-status=live}}</ref> However, there are also several other garbage collectors that can be used to manage the heap, such as the Z Garbage Collector (ZGC) introduced in Java 11, and Shenandoah GC, introduced in Java 12 but unavailable in Oracle-produced OpenJDK builds. Shenandoah is instead available in third-party builds of OpenJDK, such as ]. For most applications in Java, G1GC is sufficient. In prior versions of Java, such as Java 8, the was used as the default garbage collector. | |||
Portability is a technically difficult goal to achieve, and Java's success at that goal has been mixed. Although it is indeed possible to write programs for the Java platform that behave consistently across many host platforms, the large number of available platforms with small errors or inconsistencies led some to parody Sun's "]" slogan as "Write once, ] everywhere". | |||
Having solved the memory management problem does not relieve the programmer of the burden of handling properly other kinds of resources, like network or database connections, file handles, etc., especially in the presence of exceptions. | |||
Platform-independent Java is however very successful with server-side applications, such as ]s, ]s, and ], as well as with ]s based on ], using ] environments. | |||
== Syntax == | |||
===Automatic garbage collection=== | |||
{{Main|Java syntax}} | |||
One possible argument against languages such as ] is the burden of having to perform manual ]. In C++, memory is allocated by the programmer to create an object, then deallocated to delete the object. If a programmer forgets or is unsure when to deallocate, this can lead to a ], where a program consumes more and more memory without cleaning up after itself. Even worse, if a region of memory is deallocated twice, the program can become unstable and will likely crash. | |||
].]] | |||
The syntax of Java is largely influenced by ] and ]. Unlike C++, which combines the syntax for structured, generic, and object-oriented programming, Java was built almost exclusively as an object-oriented language.<ref name="design_goals" /> All code is written inside classes, and every data item is an object, with the exception of the primitive data types, (i.e. integers, floating-point numbers, ], and characters), which are not objects for performance reasons. Java reuses some popular aspects of C++ (such as the {{java|printf}} method). | |||
Unlike C++, Java does not support ]<ref name="msdn_operator_overloading">{{cite web |url=http://msdn.microsoft.com/en-us/library/ms228498%28v=vs.90%29.aspx |title=Operator Overloading (C# vs Java) |publisher=Microsoft |work=C# for Java Developers |access-date=December 10, 2014 |archive-url=https://web.archive.org/web/20150107190007/http://msdn.microsoft.com/en-us/library/ms228498(v=vs.90).aspx |archive-date=January 7, 2015 |url-status=live}}</ref> or ] for classes, though multiple inheritance is supported for ].<ref name="oracle_multiple_inheritance">{{cite web |url=https://docs.oracle.com/javase/tutorial/java/IandI/multipleinheritance.html |title=Multiple Inheritance of State, Implementation, and Type |publisher=Oracle |work=The Java Tutorials |access-date=December 10, 2014 |archive-url=https://web.archive.org/web/20141109034520/https://docs.oracle.com/javase/tutorial/java/IandI/multipleinheritance.html |archive-date=November 9, 2014 |url-status=live}}</ref> | |||
In Java, this potential problem is avoided by ]. Objects are created and placed at an address on the ]. The program or other objects can reference an object by holding a reference to its address on the heap. When no references to an object remain, the Java garbage collector automatically deletes the object, freeing memory and preventing a ]. Memory leaks, however, can still occur if a programmer's code holds a reference to an object that is no longer needed—in other words, they can still occur but at higher conceptual levels. But on the whole, Java's automatic garbage collection makes creation and deletion of objects in Java simpler, potentially safer, and often faster than in C++. | |||
Java uses ] similar to those of C++. There are three different styles of comments: a single line style marked with two slashes (<code>//</code>), a multiple line style opened with <code>/*</code> and closed with <code>*/</code>, and the ] commenting style opened with <code>/**</code> and closed with <code>*/</code>. The Javadoc style of commenting allows the user to run the Javadoc executable to create documentation for the program and can be read by some ]s (IDEs) such as ] to allow developers to access documentation within the IDE. | |||
Garbage collection in Java is virtually invisible to the developer. That is, developers may have no notion of when garbage collection will take place as it is not necessarily a function of the code they themselves write. | |||
== |
=== Hello world === | ||
The following is a simple example of a ] that writes a message to the ]: | |||
<syntaxhighlight lang="java" line="1">public class Example { | |||
public static void main(String args) { | |||
System.out.println("Hello World!"); | |||
} | |||
}</syntaxhighlight> | |||
== Special classes == | |||
Java was intended to serve as a novel way to manage software complexity. Most consider Java technology to deliver reasonably well on this promise. However, Java is not without flaws, and it does not universally accommodate all programming styles, environments, or requirements. | |||
{{more citations needed|section|date=May 2019}} | |||
* Not all projects or environments require enterprise-level complexity, such as stand-alone websites or sole-proprietorship programmers. Such individuals find Java's self-enforcing complexity management to be overkill. | |||
* Java is often a focal point of discontent for those who are not enthusiastic about object-oriented programming. | |||
* Java can be considered a less pure object-oriented programming language than for instance ] or ] because it makes certain compromises (such as the fact that not all values are objects) for performance reasons. | |||
* Java programs may have lower performance than those written in languages such as ], which are compiled directly into machine code. The reasons for this include the following: Java byte code is not optimized to the same degree as machine code resulting from C++; Java does not support manual ] (though many JIT compilers perform this optimization); and the usage of a ] to automatically decide when to delete objects is more expensive than imperative deletion in C++ (although modern garbage collectors may outperform imperative deletion). | |||
* As an established technology, Java inevitably invites comparison with contemporary languages such as ], ], ], and others. Commenting upon Java's proprietary nature, supposed inflexibility to change, and growing entrenchment in the corporate sector, some have said that Java is "the new ]". Many consider this to be a somewhat hyperbolic assertion, although it does allude to some legitimate concerns with Java's prospects for the future. | |||
=== |
=== Applet === | ||
{{Main|Java applet}} | |||
* The distinction between reference types and primitive types may be viewed as artificial by programmers who are familiar with languages such as ], ] and ], where everything is an object. | |||
Java applets are programs ] in other applications, mainly in web pages displayed in web browsers. The Java applet API was deprecated with the release of Java 9 in 2017.<ref>{{Cite web |url=https://www.oracle.com/technetwork/java/javase/9-deprecated-features-3745636.html#JDK-8074165|title=Deprecated APIs, Features, and Options| publisher=Oracle |access-date=2019-05-31|archive-date=June 19, 2019|archive-url=https://web.archive.org/web/20190619200811/https://www.oracle.com/technetwork/java/javase/9-deprecated-features-3745636.html#JDK-8074165|url-status=live}}</ref><ref>{{Cite web|title=Applet (Java Platform SE 7)|url=https://docs.oracle.com/javase/7/docs/api/java/applet/Applet.html|website=Docs |publisher=Oracle |access-date=2020-05-01 |archive-date=August 2, 2020 |archive-url=https://web.archive.org/web/20200802033524/https://docs.oracle.com/javase/7/docs/api/java/applet/Applet.html |url-status=live}}</ref> | |||
=== Servlet === | |||
* Conversely, ] programmers can become confused with Java because in Java primitives are always ] and objects always reside on the ], whereas ] programmers are explicitly given the choice in both cases by means of ]. | |||
{{Main|Java servlet}} | |||
] technology provides Web developers with a simple, consistent mechanism for extending the functionality of a Web server and for accessing existing business systems. Servlets are ] Java EE components that generate responses to requests from ]. Most of the time, this means generating ] pages in response to ] requests, although there are a number of other standard servlet classes available, for example for ] communication. | |||
The Java servlet API has to some extent been superseded (but still used under the hood) by two standard Java technologies for web services: | |||
* Java code is often more verbose than code written in other languages. This is due in part to its frequent type declarations and manual casts. It is also due to the lack of ] (see below) and the relatively simple syntax. However, J2SE 5.0 introduced ] which addresses the issue of manual casts, as well as new syntax for for-loops which also reduces verbosity. | |||
* the ] (JAX-RS 2.0) useful for AJAX, JSON and REST services, and | |||
* the ] (JAX-WS) useful for ] ]s. | |||
Typical implementations of these APIs on Application Servers or Servlet Containers use a standard servlet for handling all interactions with the ] requests and responses that delegate to the web service methods for the actual business logic. | |||
* Unlike ], Java does not support user-definable ]; however, this is a deliberate design decision, seen by many as a plus because of the well-known readability and ] problems experienced with operator overloading. | |||
=== JavaServer Pages === | |||
* Java is predominantly a single-paradigm language. Historically, it has not been very accommodating of paradigms other than object-oriented programming. As of J2SE 5.0, the procedural paradigm is somewhat better supported in Java with the addition of the ability to ''import static'' methods and fields so that they can be used globally as one could do in, for example, ]. | |||
{{Main|JavaServer Pages}} | |||
JavaServer Pages (]) are ] Java EE components that generate responses, typically ] pages, to ] requests from ]. JSPs embed Java code in an HTML page by using the special ]s <code><%</code> and <code>%></code>. A JSP is compiled to a Java ''servlet'', a Java application in its own right, the first time it is accessed. After that, the generated servlet creates the response.<ref>{{Cite web|title=What Is a JSP Page? - The Java EE 5 Tutorial|url=https://docs.oracle.com/javaee/5/tutorial/doc/bnagy.html|website=docs.oracle.com|access-date=2020-05-01|archive-date=August 2, 2020|archive-url=https://web.archive.org/web/20200802003029/https://docs.oracle.com/javaee/5/tutorial/doc/bnagy.html|url-status=live}}</ref> | |||
=== Swing application === | |||
* Java only supports ] of implementation. This causes consternation to programmers accustomed to orthogonal ], which is available in many other languages. However, Java employs ]s, which allow multiple inheritance of type and ]s. | |||
{{Main|Swing (Java)}} | |||
] is a graphical user interface ] for the Java SE platform. It is possible to specify a different look and feel through the ] system of Swing. Clones of ], ], and ] are supplied by Sun. ] also provides an ] look and feel for ]. Where prior implementations of these looks and feels may have been considered lacking, Swing in Java SE 6 addresses this problem by using more native ] drawing routines of the underlying platforms.<ref>{{Cite web|title=Trail: Creating a GUI With JFC/Swing (The Java Tutorials)|url=https://docs.oracle.com/javase/tutorial/uiswing/|website=docs.oracle.com|access-date=2020-05-01|archive-date=April 29, 2020|archive-url=https://web.archive.org/web/20200429104302/https://docs.oracle.com/javase/tutorial/uiswing/|url-status=live}}</ref> | |||
=== JavaFX application === | |||
* Java's support of text matching and manipulation is not as strong as languages such as ] or ], although ]s were introduced in J2SE 1.4. | |||
{{Main|JavaFX}} | |||
] is a ] for creating and delivering ], as well as ]s that can run across a wide variety of devices. JavaFX is intended to replace ] as the standard ] (GUI) library for ], but since JDK 11 JavaFX has not been in the core JDK and instead in a separate module.<ref>{{Cite web|title=Removed from JDK 11, JavaFX 11 arrives as a standalone module |work=InfoWorld |date=September 20, 2018 |url=https://www.infoworld.com/article/3305073/removed-from-jdk-11-javafx-11-arrives-as-a-standalone-module.html|access-date=2020-10-13|archive-date=October 14, 2020|archive-url=https://web.archive.org/web/20201014141716/https://www.infoworld.com/article/3305073/removed-from-jdk-11-javafx-11-arrives-as-a-standalone-module.html|url-status=live}}</ref> JavaFX has support for ]s and ]s on ], ], and ]. JavaFX does not have support for native OS look and feels.<ref>{{Cite web|title=Getting Started with JavaFX: Hello World, JavaFX Style |work=JavaFX 2 Tutorials and Documentation|url=https://docs.oracle.com/javafx/2/get_started/hello_world.htm |publisher=Oracle |access-date=2020-05-01|archive-date= August 2, 2020 |archive-url=https://web.archive.org/web/20200802013650/https://docs.oracle.com/javafx/2/get_started/hello_world.htm|url-status=live}}</ref> | |||
=== |
=== Generics === | ||
{{Main|Generics in Java}} | |||
The look and feel of GUI applications written in Java using the ] platform is often different from native applications. While programmers can choose to use the ] that displays native widgets (and thus look like the operating platform), the AWT toolkit is unable to meet advanced GUI programming needs by wrapping around advanced widgets and not sacrificing portability across the various supported platforms, each of which have vastly different APIs especially for higher-level widgets. The Swing toolkit, written completely in Java, avoids this problem by reimplementing widgets using only the most basic drawing mechanisms that are guaranteed available on all platforms. The drawback is that extra effort is required to resemble the operating platform. While this is possible (using the GTK+ and Windows Look-and-Feel), most users do not know how to change the default Metal Look-And-Feel to one that resembles their native platform, and as a result they are stuck with Java applications that look radically different from their native applications. Of note however, Apple Computer's own optimized version of the Java Runtime, which is included within the Mac OS X distribution, by default implements its "Aqua" Look-And-Feel, giving Swing applications a similar appearance to native Mac software. | |||
In 2004, ] were added to the Java language, as part of J2SE 5.0. Prior to the introduction of generics, each variable declaration had to be of a specific type. For container classes, for example, this is a problem because there is no easy way to create a container that accepts only specific types of objects. Either the container operates on all subtypes of a class or interface, usually <code>Object</code>, or a different container class has to be created for each contained class. Generics allow compile-time type checking without having to create many container classes, each containing almost identical code. In addition to enabling more efficient code, certain runtime exceptions are prevented from occurring, by issuing compile-time errors. If Java prevented all runtime type errors (<code>ClassCastException</code>s) from occurring, it would be ]. | |||
Some parts of the standard Java libraries are considered excessively complicated, or badly designed, but cannot be changed due to the need for backward compatibility. | |||
In 2016, the type system of Java was proven ] in that it is possible to use generics to construct classes and methods that allow assignment of an instance of one class to a variable of another unrelated class. Such code is accepted by the compiler, but fails at run time with a class cast exception.<ref>{{cite web|url=https://raw.githubusercontent.com/namin/unsound/master/doc/unsound-oopsla16.pdf|title=Java and Scala's Type Systems are Unsound|access-date=February 20, 2017 |archive-url=https://web.archive.org/web/20161128174902/https://raw.githubusercontent.com/namin/unsound/master/doc/unsound-oopsla16.pdf |archive-date=November 28, 2016|url-status=live}}</ref> | |||
===Performance=== | |||
It is misleading to make any generalization about the performance of Java programs in general, because run-time performance is affected much more by the quality of the compiler or JVM than by any intrinsic properties of the language itself. | |||
== Criticism == | |||
Indeed, there are very few language requirements which incur an unavoidable time penalty. Among these are array bounds checking, run-time type checking and virtual function indirection, all of which can be made much cheaper by a good compiler or JVM. ] may actually increase the performance of some programs, if implemented well. | |||
{{Main|Criticism of Java}} | |||
Criticisms directed at Java include the implementation of generics,<ref>{{cite web | |||
|last=Arnold | |||
|first=Ken | |||
|date=June 27, 2005 | |||
|title=Generics Considered Harmful | |||
|url=https://weblogs.java.net/blog/arnold/archive/2005/06/generics_consid_1.html | |||
|publisher=java.net | |||
|access-date=September 10, 2015 | |||
|url-status=dead | |||
|archive-url=https://web.archive.org/web/20071010002142/http://weblogs.java.net/blog/arnold/archive/2005/06/generics_consid_1.html | |||
|archive-date=October 10, 2007 | |||
}}</ref> speed,<ref name=Jelovic /> the handling of unsigned numbers,<ref>{{cite web | |||
|last=Owens |first=Sean R. | |||
|url=http://darksleep.com/player/JavaAndUnsignedTypes.html | |||
|archive-url=https://web.archive.org/web/20090220171410/http://darksleep.com/player/JavaAndUnsignedTypes.html | |||
|archive-date=February 20, 2009 | |||
|title=Java and unsigned int, unsigned short, unsigned byte, unsigned long, etc. (Or rather, the lack thereof) | |||
|access-date=2011-07-04 | |||
}}</ref> the implementation of floating-point arithmetic,<ref>{{cite web | |||
|last=Kahan | |||
|first=William | |||
|date=March 1, 1998 | |||
|title=How Java's Floating-Point Hurts Everyone Everywhere – ACM 1998 Workshop on Java (Stanford) | |||
|url=http://www.cs.berkeley.edu/~wkahan/JAVAhurt.pdf | |||
|publisher=Electrical Engineering & Computer Science, University of California at Berkeley | |||
|access-date=June 4, 2011 | |||
|archive-url=https://web.archive.org/web/20120905004527/http://www.cs.berkeley.edu/~wkahan/JAVAhurt.pdf | |||
|archive-date=September 5, 2012 | |||
|url-status=live | |||
}}</ref> and a history of security vulnerabilities in the primary Java VM implementation ].<ref>{{cite web | |||
|url=http://blogs.technet.com/b/mmpc/archive/2010/10/18/have-you-checked-the-java.aspx | |||
|title=Have you checked the Java? | |||
|access-date=December 23, 2011 | |||
|archive-url=https://web.archive.org/web/20120921140402/http://blogs.technet.com/b/mmpc/archive/2010/10/18/have-you-checked-the-java.aspx | |||
|archive-date=September 21, 2012 | |||
|url-status=dead | |||
}}</ref> | |||
Developers have criticized the complexity and verbosity of the Java Persistence API (JPA), a standard part of Java EE. This has led to increased adoption of higher-level abstractions like Spring Data JPA, which aims to simplify database operations and reduce boilerplate code. The growing popularity of such frameworks suggests limitations in the standard JPA implementation's ease-of-use for modern Java development.<ref>{{cite book | |||
|last=Chidester | |||
|first=Ashlan | |||
|title=Java Persistence API, Jenkins and AWS | |||
|url=https://www.vlebooks.com/vleweb/product/openreader?id=none&isbn=9798224253951 | |||
|access-date=September 16, 2024 | |||
|isbn=9798224253951 | |||
}}</ref> | |||
== Class libraries == | |||
Relative performance of JIT compilers as compared to native compilers can be quite close (often superseeding native compiled), and is often a subject of debate. The JIT stage may be time-consuming, which is inconvenient for applications that are short-lived and/or contain large amounts of code. Once this is done, however, the performance of the program can easily be comparable to that achieved by a native compiler, even on numerical tasks. In addition, JITs can exploit information from the runtime environment to guide more effective transformations, such as profile-directed inlining. | |||
{{Main|Java Class Library}} | |||
The ] is the ], developed to support application development in Java. It is controlled by ] in cooperation with others through the ] program.<ref>{{Citation|last=Cadenhead|first=Rogers|title=Understanding How Java Programs Work|date=2017-11-20|url=http://www.informit.com/articles/article.aspx?p=2832404&seqNum=4|access-date=2019-03-26|archive-date=August 13, 2021|archive-url=https://web.archive.org/web/20210813193850/https://www.informit.com/articles/article.aspx?p=2832404&seqNum=4|url-status=live}}</ref> Companies or individuals participating in this process can influence the design and development of the APIs. This process has been a subject of controversy during the 2010s.<ref>{{Cite news|url=https://www.theguardian.com/technology/2016/may/26/google-wins-copyright-lawsuit-oracle-java-code|title=Google wins six-year legal battle with Oracle over Android code copyright|last=Woolf|first=Nicky|date=2016-05-26|work=The Guardian|access-date=2019-03-26|language=en-GB|issn=0261-3077|archive-date=March 26, 2019|archive-url=https://web.archive.org/web/20190326203847/https://www.theguardian.com/technology/2016/may/26/google-wins-copyright-lawsuit-oracle-java-code|url-status=live}}</ref> The class library contains features such as: | |||
Java was designed with an emphasis on security and portability, and does not support direct access to the machine architecture and address space. Applications can drop down to native code to access these features using the ] (JNI). | |||
* The core libraries, which include: | |||
** ] (I/O or IO){{sfn|Bloch|2018|loc=§ 1 Introduction|pp=1-4}} and ] (NIO), or IO/NIO<ref>{{Cite web|url=https://docs.oracle.com/javase/8/docs/api/java/nio/package-summary.html|title=java.nio (Java Platform SE 8)|website=docs.oracle.com}}</ref> | |||
==Syntax== | |||
** ]<ref>{{Cite web|url=https://docs.oracle.com/javase/8/docs/technotes/guides/net/|title=Java Networking|website=docs.oracle.com}}</ref> (new ] (HTTP client) since Java 11<ref>{{Cite web|url=https://docs.oracle.com/en/java/javase/11/docs/api/java.net.http/java/net/http/HttpClient.html|title=HttpClient (Java SE 11 & JDK 11)|website=docs.oracle.com}}</ref>) | |||
** ] (reflection) | |||
:''Main article: ]'' | |||
** ] (concurrency){{sfn|Bloch|2018|loc=§ 1 Introduction|pp=1-4}} | |||
** ] | |||
The syntax of Java is largely derived from C++. But unlike C++, which combines the syntax for procedural and object-oriented programming, Java was built from the ground up to be fully object-oriented. Everything in Java is an object (with a few exceptions), and everything in Java is written inside a class. | |||
** Scripting, Compiler | |||
** ] (], streaming) | |||
===Hello world=== | |||
** ] that implement ]s such as ], ], ], ], ] and ], or ]<ref name="collections">{{cite web |url=http://docs.oracle.com/javase/8/docs/technotes/guides/collections/overview.html |title=Collections Framework Overview |publisher=Oracle |work=Java Documentation |access-date=December 18, 2014 |archive-url=https://web.archive.org/web/20141231132540/http://docs.oracle.com/javase/8/docs/technotes/guides/collections/overview.html |archive-date=December 31, 2014 |url-status=live}}</ref> | |||
** ] Processing (Parsing, Transforming, Validating) libraries | |||
:''For an explanation of the tradition of programming "Hello World", see ].'' | |||
** ]<ref name="security">{{cite web |url=http://docs.oracle.com/javase/8/docs/technotes/guides/security/overview/jsoverview.html |title=Java Security Overview |publisher=Oracle |work=Java Documentation |access-date=December 18, 2014 |archive-url=https://web.archive.org/web/20150103045031/http://docs.oracle.com/javase/8/docs/technotes/guides/security/overview/jsoverview.html |archive-date=January 3, 2015 |url-status=live}}</ref> | |||
** ] libraries<ref name="i18n">{{cite web |url=http://docs.oracle.com/javase/tutorial/i18n/ |title=Trail: Internationalization |publisher=Oracle |work=The Java Tutorials |access-date=December 18, 2014 |archive-url=https://web.archive.org/web/20141231053232/http://docs.oracle.com/javase/tutorial/i18n/ |archive-date=December 31, 2014 |url-status=live}}</ref> | |||
====Stand-alone app==== | |||
* The integration libraries, which allow the application writer to communicate with external systems. These libraries include: | |||
** The ] (JDBC) ] for database access | |||
// Hello.java | |||
** ] (JNDI) for lookup and discovery | |||
public class Hello { | |||
** ] (RMI) and ] (CORBA) for distributed application development | |||
public static void main(String args) { | |||
** ] (JMX) for managing and monitoring applications | |||
System.out.println("Hello, world!"); | |||
* ] libraries, which include: | |||
} | |||
** The (heavyweight, or ]) ] (AWT), which provides ] components, the means for laying out those components and the means for handling events from those components | |||
} | |||
** The (lightweight) ] libraries, which are built on AWT but provide (non-native) implementations of the AWT widgetry | |||
** APIs for audio capture, processing, and playback | |||
The above example merits a bit of explanation for those accustomed to languages with inherently relaxed security, weak typing, and weak object orientation. | |||
** ] | |||
* Everything in Java is written inside a class, including stand-alone programs. | |||
* A platform dependent implementation of the Java virtual machine that is the means by which the bytecodes of the Java libraries and third-party applications are executed | |||
* Source files are by convention named the same as the class they contain, appending the mandatory suffix ''.java''. A <code>'''class'''</code> which is declared <code>'''public'''</code> is required to follow this convention. (In this case, the class is <code>'''Hello'''</code>, therefore the source must be stored in a file called ''Hello.java''). | |||
* Plugins, which enable ] to be run in web browsers | |||
* The compiler will generate a class file for each class defined in the source file. The name of the class file is the name of the class, with ''.class'' appended. For class file generation, anonymous classes are treated as if their name was the concatenation of the name of their enclosing class, a ''$'', and an integer. | |||
* ], which allows Java applications to be efficiently distributed to ]s across the Internet | |||
* Programs to be executed as stand-alone must have a <code>'''main()'''</code> method. | |||
* The ] <code>'''void'''</code> indicates that the main method does not return anything. | |||
* The main method must accept an ] of '''{{Javadoc:SE|java/lang|String}}''' objects. By convention, it is referenced as <code>'''args'''</code> although any other legal identifier name can be used. | |||
* The keyword <code>'''static'''</code> indicates that the method is a ], associated with the class rather than object instances. Main methods must be static. | |||
* The keyword <code>'''public'''</code> denotes that a method can be called from code in other classes, or that a class may be used by classes outside the class hierarchy. Main methods must also be public. | |||
* The printing facility is part of the Java standard library: The '''{{Javadoc:SE|java/lang|System}}''' class defines a public static field called '''{{Javadoc:SE|name=out|java/lang|System|out}}'''. The <code>out</code> object is an instance of the {{Javadoc:SE|java/io|PrintStream}} class and provides the method '''{{Javadoc:SE|name=println(String)|java/io|PrintStream|println(java.lang.String)}}''' for displaying data to the screen (]). | |||
* Standalone programs are run by giving the Java runtime the name of the class whose main method is to be invoked. For example, at a ] command line <code>java -cp . Hello</code> will start the above program (compiled into ''Hello.class'') from the current directory. The name of the class whose main method is to be invoked can also be specified in the ''MANIFEST'' of a ]. | |||
====Applet==== | |||
]s are programs that are embedded in other applications, typically in a Web page displayed in a ]. | |||
// Hello.java | |||
import java.applet.Applet; | |||
import java.awt.Graphics; | |||
public class Hello extends Applet { | |||
public void paint(Graphics gc) { | |||
gc.drawString("Hello, world!", 65, 95); | |||
} | |||
} | |||
<!-- Hello.html --> | |||
<html> | |||
<head> | |||
<title>Hello World Applet</title> | |||
</head> | |||
<body> | |||
<applet code="Hello" width="200" height="200"> | |||
</applet> | |||
</body> | |||
</html> | |||
The '''<code>import</code>''' statements direct the ] to include the '''{{Javadoc:SE|package=java.applet|java/applet|Applet}}''' and '''{{Javadoc:SE|package=java.awt|java/awt|Graphics}}''' classes in the compilation. The import statement allows these classes to be referenced in the ] using the ''simple class name'' (i.e. <code>Applet</code>) instead of the ''fully-qualified class name'' (i.e. <code>java.applet.Applet</code>). | |||
The <code>'''Hello'''</code> class <code>'''extends'''</code> (]) the '''<code>Applet</code>''' class; the <code>Applet</code> class provides the framework for the host application to display and control the ] of the applet. The <code>Applet</code> class is an ] (AWT) {{Javadoc:SE|java/awt|Component}}, which provides the applet with the capability to display a ] (GUI) and respond to user ]. | |||
The <code>Hello</code> class ] the '''{{Javadoc:SE|name=paint(Graphics)|java/awt|Container|paint(java.awt.Graphics)}}''' method inherited from the {{Javadoc:SE|java/awt|Container}} ] to provide the code to display the applet. The <code>paint()</code> method is passed a '''<code>Graphics</code>''' object that contains the graphic context used to display the applet. The <code>paint()</code> method calls the graphic context '''{{Javadoc:SE|name=drawString(String, int, int)|java/awt|Graphics|drawString(java.lang.String,%20int,%20int)}}''' method to display the '''"Hello, world!"''' string at a ] offset of (65,95) in the applet. | |||
An applet is placed in an ] document using the '''<code><applet></code>''' ]. The <code>applet</code> tag has three attributes set: '''<code>code="Hello"</code>''' specifies the name of the <code>Applet</code> class and '''<code>width="200" height="200"</code>''' sets the pixel width and height of the applet. (Applets may also be embedded in HTML using either the <code>object</code> or <code>embed</code> element, although support for these elements by Web browsers is inconsistent.) | |||
====Servlet==== | |||
]s are ] Java EE components that generate responses to requests from ]s. | |||
// Hello.java | |||
import java.io.*; | |||
import javax.servlet.*; | |||
public class Hello extends GenericServlet { | |||
public void service(ServletRequest request, ServletResponse response) | |||
throws ServletException, IOException | |||
{ | |||
response.setContentType("text/html"); | |||
PrintWriter pw = response.getWriter(); | |||
pw.println("Hello, world!"); | |||
pw.close(); | |||
} | |||
} | |||
The '''<code>import</code>''' statements direct the Java compiler to include all of the public classes and ] from the '''{{Javadoc:SE|package=java.io|java/io}}''' and '''{{Javadoc:EE|package=javax.servlet|javax/servlet}}''' ] in the compilation. | |||
The <code>'''Hello'''</code> class <code>'''extends'''</code> the '''{{Javadoc:EE|javax/servlet|GenericServlet}}''' class; the <code>GenericServlet</code> class provides the interface for the ] to forward requests to the servlet and control the servlet's lifecycle. | |||
The <code>Hello</code> class overrides the '''{{Javadoc:EE|name=service(ServletRequest, ServletResponse)|javax/servlet|Servlet|service(javax.servlet.ServletRequest,javax.servlet.ServletResponse)}}''' method defined by the {{Javadoc:EE|javax/servlet|Servlet}} ] to provide the code for the service request handler. The <code>service()</code> method is passed a '''{{Javadoc:EE|javax/servlet|ServletRequest}}''' object that contains the request from the client and a '''{{Javadoc:EE|javax/servlet|ServletResponse}}''' object used to create the response returned to the client. The <code>service()</code> method declares that it <code>'''throws'''</code> the ] {{Javadoc:EE|javax/servlet|ServletException}} and {{Javadoc:SE|java/io|IOException}} if a problem prevents it from responding to the request. | |||
The '''{{Javadoc:EE|name=setContentType(String)|javax/servlet|ServletResponse|setContentType(java.lang.String)}}''' method in the response object is called to set the ] content type of the returned data to '''"text/html"'''. The '''{{Javadoc:EE|name=getWriter()|javax/servlet|ServletResponse|getWriter()}}''' method in the response returns a '''{{Javadoc:SE|java/io|PrintWriter}}''' object that is used to write the data that is sent to the client. The '''{{Javadoc:SE|name=println(String)|java/io|PrintWriter|println(java.lang.String)}}''' method is called to write the '''"Hello, world!"''' string to the response and then the '''{{Javadoc:SE|name=close()|java/io|PrintWriter|close()}}''' method is called to close the print writer, which causes the data that has been written to the stream to be returned to the client. | |||
====Swing==== | |||
] is the advanced graphical user interface ] for the Java SE platform. | |||
// Hello.java | |||
import javax.swing.*; | |||
public class Hello extends JFrame { | |||
Hello() { | |||
setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE); | |||
add(new JLabel("Hello, world!")); | |||
pack(); | |||
} | |||
public static void main(String args) { | |||
new Hello().setVisible(true); | |||
} | |||
} | |||
The '''<code>import</code>''' statement directs the Java compiler to include all of the public classes and interfaces from the '''{{Javadoc:SE|package=javax.swing|javax/swing}}''' package in the compilation. | |||
The <code>'''Hello'''</code> class <code>'''extends'''</code> the '''{{Javadoc:SE|javax/swing|JFrame}}''' class; the <code>JFrame</code> class implements a ] with a ] with a close ]. | |||
The <code>'''Hello()'''</code> ] initializes the frame by first calling the '''{{Javadoc:SE|name=setDefaultCloseOperation(int)|javax/swing|JFrame|setDefaultCloseOperation(int)}}''' method inherited from <code>JFrame</code> to set the default operation when the close control on the title bar is selected to <code>'''{{Javadoc:SE|javax/swing|WindowConstants|DISPOSE_ON_CLOSE}}'''</code>—this causes the <code>JFrame</code> to be disposed of when the frame is closed (as opposed to merely hidden), which allows the JVM to exit and the program to terminate. Next a '''<code>new </code>{{Javadoc:SE|javax/swing|JLabel}}''' is created for the string '''"Hello, world!"''' and the '''{{Javadoc:SE|name=add(Component)|java/awt|Container|add(java.awt.Component)}}''' method inherited from the {{Javadoc:SE|java/awt|Container}} superclass is called to add the label to the frame. The '''{{Javadoc:SE|name=pack()|java/awt|Window|pack()}}''' method inherited from the {{Javadoc:SE|java/awt|Window}} superclass is called size the window and ] its contents. | |||
The <code>'''main()'''</code> method is called by the JVM when the program starts. It ] a '''<code>new Hello</code>''' frame and causes it to be displayed by calling the '''{{Javadoc:SE|name=setVisible(boolean)|java/awt|Component|setVisible(boolean)}}''' method inherited from the {{Javadoc:SE|java/awt|Component}} superclass with the boolean parameter <code>'''true'''</code>. Note that once the frame is displayed, exitting the <code>main</code> method does not cause the program to terminate because the AWT ] remains active until all of the Swing top-level windows have been disposed. | |||
==Resources== | |||
===Java Runtime Environment=== | |||
The ''']''' or '''JRE''' is the software required to run any ] deployed on the Java Platform. ]s commonly use a JRE in ]s and Web browser ]s. Sun also distributes a superset of the JRE called the Java 2 ] (more commonly known as the JDK), which includes development tools such as the Java ], ], and ]. | |||
====Components==== | |||
* Java ] - which are the compiled ]s of source developed by the JRE implementor to support application development in Java. Examples of these libraries are: | |||
** The core libraries, which include: | |||
*** Collection libraries which implement ]s such as ]s, ], ] and ] | |||
*** ] ] libraries | |||
*** Security | |||
*** ] libraries | |||
** The integration libraries, which allow the application writer to communicate with external systems. These libraries include: | |||
*** The ] (JDBC) ] for database access | |||
*** ] (JNDI) for lookup and discovery | |||
*** ] and ] for distributed application development | |||
** ] libraries, which include: | |||
*** The (heavyweight, or ]) ] (AWT), which provides ] components, the means for laying out those components and the means for handling events from those components | |||
*** The (lightweight) ] libraries, which are built on AWT but provide (non-native) implementations of the AWT widgetry | |||
*** APIs for audio capture, processing, and playback | |||
* A platform dependent implementation of ] (JVM) which is the means by which the byte codes of the Java libraries and third party applications are executed | |||
* Plugins, which enable ]s to be run in web browsers | |||
* ], which allows Java applications to be efficiently distributed to ]s across the ] | |||
* Licensing and documentation | * Licensing and documentation | ||
== |
== Documentation == | ||
{{Main|Javadoc}} | |||
Sun has defined three platforms targeting different application environments and segmented many of its ]s so that they belong to one of the platforms. The platforms are: | |||
Javadoc is a comprehensive documentation system, created by ]. It provides developers with an organized system for documenting their code. Javadoc comments have an extra asterisk at the beginning, i.e. the delimiters are <code>/**</code> and <code>*/</code>, whereas the normal multi-line comments in Java are delimited by <code>/*</code> and <code>*/</code>, and single-line comments start with <code>//</code>.<ref name="javadoc_comments">{{cite web |url=https://www.oracle.com/technetwork/articles/java/index-137868.html |title=How to Write Doc Comments for the Javadoc Tool |publisher=Oracle |work=Oracle Technology Network |access-date=December 18, 2014 |archive-url=https://web.archive.org/web/20141218182906/http://www.oracle.com/technetwork/articles/java/index-137868.html |archive-date=December 18, 2014 |url-status=live}}</ref> | |||
*] (Java ME) — targeting environments with limited resources, | |||
*] (Java SE) — targeting workstation environments, and | |||
*] (Java EE) — targeting large distributed enterprise or Internet environments. | |||
== Implementations == | |||
The ] in the Java APIs are organized into separate groups called ]. Each package contains a set of related ]s, classes and ]. Refer to the separate platforms for a description of the packages available. | |||
{{See also|Free Java implementations|List of Java compilers}} | |||
{{More citations needed|section|date=September 2023}} | |||
] owns the official implementation of the Java SE platform, due to its acquisition of ] on January 27, 2010. This implementation is based on the original implementation of Java by Sun. The Oracle implementation is available for ], ], ], and ]. Because Java lacks any formal standardization recognized by ], ISO/IEC, ANSI, or other third-party standards organizations, the Oracle implementation is the ]. | |||
The Oracle implementation is packaged into two different distributions: The Java Runtime Environment (JRE) which contains the parts of the Java SE platform required to run Java programs and is intended for end users, and the ] (JDK), which is intended for software developers and includes development tools such as the ], ], ], and a ]. Oracle has also released ], a high performance Java dynamic compiler and interpreter. | |||
The set of APIs is controlled by Sun Microsystems in cooperation with others through the ] program. Companies or individuals participating in this process can influence the design and development of the APIs. This process has been a subject of controversy. | |||
] is another Java SE implementation that is licensed under the GNU GPL. The implementation started when Sun began releasing the Java source code under the GPL. As of Java SE 7, OpenJDK is the official Java reference implementation. | |||
In 2004, IBM and BEA publicly supported the notion of creating an official open source implementation of Java but as of 2006, Sun Microsystems has refused that. | |||
The goal of Java is to make all implementations of Java compatible. Historically, Sun's trademark license for usage of the Java brand insists that all implementations be ''compatible''. This resulted in a legal dispute with ] after Sun claimed that the Microsoft implementation did not support ] (RMI) or ] (JNI) and had added platform-specific features of their own. Sun sued in 1997, and, in 2001, won a settlement of US$20 million, as well as a court order enforcing the terms of the license from Sun.<ref>{{cite news |last1=Niccolai |first1=James |date=2001-01-24 |title=Sun, Microsoft settle Java lawsuit |url=https://www.infoworld.com/article/2074908/sun-microsoft-settle-java-lawsuit.html |work=] |agency=] |access-date=2020-07-13 |archive-date=July 14, 2020 |archive-url=https://web.archive.org/web/20200714001541/https://www.infoworld.com/article/2074908/sun-microsoft-settle-java-lawsuit.html |url-status=live}}</ref> As a result, Microsoft no longer ships Java with ]. | |||
===Extensions and related architectures=== | |||
<!---------------------------------------------------------------------------------- | |||
Only list extensions and APIs developed under the Java Community Process here. | |||
-----------------------------------------------------------------------------------> | |||
The ] to standard Java are typically in <code>javax.*</code> packages. They are not included in the JDK or JRE. Extensions and architectures closely tied to the Java programming language include: | |||
*] (previously J2EE) (Java Platform, Enterprise Edition — for distributed enterprise applications) | |||
*] (previously J2ME) (Java Platform, Micro Edition — for PDAs and cellular phones) | |||
*] (Java Media Framework) | |||
*] (Java Naming and Directory Interface) | |||
*] (Java Speech API Markup Language) | |||
*] (Java Database Connectivity) | |||
*] (Java Data Objects) | |||
*] (Java Advanced Imaging) | |||
*] (Java API for Integrated Networks) | |||
*] (Java Dynamic Management Kit) | |||
*] (a network architecture for the construction of ] ]s) | |||
*] | |||
*] | |||
*] | |||
*] (Java Modeling Language) | |||
*] (Java Metadata Interface) | |||
*] (Java Management Extensions) | |||
*] (JavaServer Pages) | |||
*] (JavaServer Faces) | |||
*] (Java Native Interface) | |||
*] (Open Protocols for ] (P2P) Virtual Network) | |||
*] (Java 3D — A high level API for 3D graphics programming) | |||
*] (Java OpenGL — A low level API for 3D graphics programming, using ]) | |||
*] (Light Weight Java Game Library — A low level API providing access to ], ] and various input devices) | |||
*] (Dynamic Service Management and Remote Maintenance) | |||
<!---------------------------------------------------------------------------------- | |||
Only list extensions and APIs developed under the Java Community Process above. | |||
-----------------------------------------------------------------------------------> | |||
Platform-independent Java is essential to ], and an even more rigorous validation is required to certify an implementation. This environment enables portable server-side applications. | |||
==See also== | |||
== Use outside the Java platform == | |||
*] | |||
The Java programming language requires the presence of a software platform in order for compiled programs to be executed. | |||
*] | |||
*] | |||
*] | |||
*] | |||
*] (Java SE, J2SE) | |||
*] | |||
*] | |||
*] | |||
*] | |||
*] | |||
*] | |||
*] | |||
*] | |||
*] | |||
Oracle supplies the ] for use with Java. The ] is an alternative software platform, used primarily for developing ]s with its own GUI system. | |||
===Lists=== | |||
*] | |||
*] | |||
*] | |||
*] | |||
== |
=== Android === | ||
The Java language is a key pillar in ], an ] ]. Although Android, built on the ], is written largely in C, the ] uses the Java language as the basis for Android applications but does not use any of its standard GUI, SE, ME or other established Java standards.<ref>{{cite web | |||
* Jon Byous, . Sun Developer Network, no date . Retrieved ], ]. | |||
|url=http://www.javalobby.org/nl/archive/jlnews_20071113o.html | |||
* ], . Java.net, no date . Retrieved ], ]. | |||
|title=Google Android: Initial Impressions and Criticism | |||
* ], ], ], and ], ''The Java language specification'', third edition. Addison-Wesley, 2005. ISBN 0321246780. | |||
|date=November 13, 2007 | |||
* Tim Lindholm and Frank Yellin. ''The Java Virtual Machine specification'', second edition. Addison-Wesley, 1999. ISBN 0201432943. | |||
|last=van Gurp | |||
|first=Jilles | |||
|work=Javalobby | |||
|quote=''Frankly, I don't understand why Google intends to ignore the vast amount of existing implementation out there. It seems like a bad case of "not invented here" to me. Ultimately, this will slow adoption. There are already too many Java platforms for the mobile world and this is yet another one'' | |||
|access-date=March 7, 2009 | |||
|archive-date=August 28, 2008 | |||
|archive-url=https://web.archive.org/web/20080828111808/http://www.javalobby.org/nl/archive/jlnews_20071113o.html | |||
|url-status=usurped | |||
}}</ref> The bytecode language supported by the Android SDK is incompatible with Java bytecode and runs on its own virtual machine, optimized for low-memory devices such as ]s and ]s. Depending on the Android version, the bytecode is either interpreted by the ] or compiled into native code by the ]. | |||
Android does not provide the full Java SE standard library, although the Android SDK does include an independent implementation of a large subset of it. It supports Java 6 and some Java 7 features, offering an implementation compatible with the standard library (]). | |||
==Notes== | |||
==== Controversy ==== | |||
# {{note|star7}} The device was named '''Star7''' after a telephone feature activated by '''*7''' on a telephone keypad, which enabled users to answer the telephone anywhere. | |||
{{See also|Oracle America, Inc. v. Google, Inc.}} | |||
The use of Java-related technology in Android led to a legal dispute between Oracle and Google. On May 7, 2012, a San Francisco jury found that if APIs could be copyrighted, then Google had infringed Oracle's copyrights by the use of Java in Android devices.<ref>{{cite web |last=Mullin |first=Joe |title=Google guilty of infringement in Oracle trial; future legal headaches loom |url=https://arstechnica.com/tech-policy/news/2012/05/jury-rules-google-violated-copyright-law-google-moves-for-mistrial.ars |work=Law & Disorder |date=May 7, 2012 |publisher=Ars Technica |access-date=2012-05-08 |archive-url=https://web.archive.org/web/20120508134916/http://arstechnica.com/tech-policy/news/2012/05/jury-rules-google-violated-copyright-law-google-moves-for-mistrial.ars |archive-date=May 8, 2012 |url-status=live}}</ref> District Judge ] ruled on May 31, 2012, that APIs cannot be copyrighted,<ref>{{cite web | |||
|title=Google wins crucial API ruling, Oracle's case decimated | |||
|url=https://arstechnica.com/tech/2012/05/google-wins-crucial-api-ruling-oracles-case-decimated/ | |||
|first=Joe | |||
|last=Mullin | |||
|work=Ars Technica | |||
|date=May 31, 2012 | |||
|access-date=2012-06-01 | |||
|archive-url=https://web.archive.org/web/20170312065520/https://arstechnica.com/tech-policy/2012/05/google-wins-crucial-api-ruling-oracles-case-decimated/ | |||
|archive-date=March 12, 2017 | |||
|url-status=live | |||
}}</ref> but this was reversed by the United States Court of Appeals for the Federal Circuit in May 2014.<ref name="cnet appeals">{{cite news |url=https://www.cnet.com/news/court-sides-with-oracle-over-android-in-java-patent-appeal/ |title=Court sides with Oracle over Android in Java patent appeal |work=CNET |date=May 9, 2014 |access-date=2014-05-10 |author=Rosenblatt, Seth |archive-url=https://web.archive.org/web/20140510203805/http://www.cnet.com/news/court-sides-with-oracle-over-android-in-java-patent-appeal/ |archive-date=May 10, 2014 |url-status=live}}</ref> On May 26, 2016, the district court decided in favor of Google, ruling the copyright infringement of the Java API in Android constitutes fair use.<ref>{{cite web |last1=Mullin |first1=Joe |title=Google beats Oracle—Android makes "fair use" of Java APIs |url=https://arstechnica.com/tech-policy/2016/05/google-wins-trial-against-oracle-as-jury-finds-android-is-fair-use/ |access-date=2016-05-26 |website=Ars Technica |date=2016-05-26 |archive-url=https://web.archive.org/web/20170120164551/http://arstechnica.com/tech-policy/2016/05/google-wins-trial-against-oracle-as-jury-finds-android-is-fair-use/ |archive-date=January 20, 2017 |url-status=live}}</ref> In March 2018, this ruling was overturned by the Appeals Court, which sent down the case of determining the damages to federal court in San Francisco.<ref>{{cite web | |||
|title="Google's use of the Java API packages was not fair," appeals court rules | |||
|url=https://arstechnica.com/tech-policy/2018/03/googles-use-of-the-java-api-packages-was-not-fair-appeals-court-rules/ | |||
|first=Cyrus | |||
|last=Farivar | |||
|work=Ars Technica | |||
|date=March 27, 2018 | |||
|access-date=2019-08-06 | |||
|archive-date=September 24, 2019 | |||
|archive-url=https://web.archive.org/web/20190924081919/https://arstechnica.com/tech-policy/2018/03/googles-use-of-the-java-api-packages-was-not-fair-appeals-court-rules/ | |||
|url-status=live | |||
}}</ref> | |||
Google filed a petition for ] with the ] in January 2019 to challenge the two rulings that were made by the Appeals Court in Oracle's favor.<ref>{{cite web |url=https://arstechnica.com/tech-policy/2019/01/google-asks-supreme-court-to-overrule-disastrous-ruling-on-api-copyrights/ |title=Google asks Supreme Court to overrule disastrous ruling on API copyrights |first=Timothy |last=Lee |date=April 23, 2019 |access-date=April 23, 2019 |work=] |archive-date=April 23, 2019 |archive-url=https://web.archive.org/web/20190423084450/https://arstechnica.com/tech-policy/2019/01/google-asks-supreme-court-to-overrule-disastrous-ruling-on-api-copyrights/ |url-status=live}}</ref> On April 5, 2021, the Court ruled 6–2 in Google's favor, that its use of Java APIs should be considered ]. However, the court refused to rule on the copyrightability of APIs, choosing instead to determine their ruling by considering Java's API copyrightable "purely for argument's sake."<ref>{{Cite web |url=https://www.supremecourt.gov/opinions/20pdf/18-956_d18f.pdf |title=''Google LLC v. Oracle America, Inc'' 593 U. S. ____ (2021) |access-date=April 6, 2021 |archive-date=April 5, 2021 |archive-url=https://web.archive.org/web/20210405140150/https://www.supremecourt.gov/opinions/20pdf/18-956_d18f.pdf |url-status=live}}</ref> | |||
== |
== See also == | ||
{{Portal|Computer programming}} | |||
* ] | |||
* ] | |||
* ], used in old Android versions, replaced by non-JIT ] | |||
* ] | |||
* ] | |||
* ] | |||
* ] | |||
* ] | |||
* ] | |||
* ] | |||
* ] | |||
== References == | |||
{{Wikibookspar|Programming|Java}} | |||
{{Reflist}} | |||
== |
== Bibliography == | ||
{{refbegin}} | |||
* | |||
* {{cite book | title="Effective Java: Programming Language Guide" |last=Bloch| first=Joshua| publisher=Addison-Wesley | edition=third | isbn=978-0-13-468599-1| year=2018}} | |||
* Authoritative description of the Java language (also available ) | |||
* {{cite book |last1=Gosling |first1=James |last2=Joy |first2=Bill |last3=Steele |first3=Guy |last4=Bracha |first4=Gilad |last5=Buckley |first5=Alex |title=The Java® Language Specification |date=2014 |edition=Java SE 8 |url=https://docs.oracle.com/javase/specs/jls/se8/jls8.pdf |access-date=November 18, 2014 |archive-date=October 21, 2014 |archive-url=https://web.archive.org/web/20141021061951/http://docs.oracle.com/javase/specs/jls/se8/jls8.pdf |url-status=live}} | |||
* {{Javadoc:SE}} | |||
* {{cite book |last1=Gosling |first1=James |last2=Joy |first2=Bill |author-link2=Bill Joy |last3=Steele |first3=Guy L. Jr. |author-link3=Guy L. Steele, Jr. |first4=Gilad |last4=Bracha |author-link4=Gilad Bracha |year=2005 |title=The Java Language Specification |url=https://java.sun.com/docs/books/jls/ |edition=3rd |publisher=Addison-Wesley |isbn=0-321-24678-0 |access-date=February 8, 2019 |archive-date=February 14, 2012 |archive-url=https://web.archive.org/web/20120214061826/http://java.sun.com/docs/books/jls/ |url-status=live}} | |||
* | |||
* {{cite book |last1=Lindholm |first1=Tim |last2=Yellin |first2=Frank |year=1999 |title=The Java Virtual Machine Specification |url=https://java.sun.com/docs/books/vmspec/2nd-edition/html/VMSpecTOC.doc.html |edition=2nd |publisher=Addison-Wesley |isbn=0-201-43294-3 |access-date=February 8, 2019 |archive-date=September 25, 2011 |archive-url=https://web.archive.org/web/20110925050249/http://java.sun.com/docs/books/vmspec/2nd-edition/html/VMSpecTOC.doc.html |url-status=live}} | |||
* , 1996 | |||
{{refend}} | |||
* | |||
== External links == | |||
===]s=== | |||
{{Sister project links |wikt=Java |display=Java |commons=Category:Java (programming language) |b=Java Programming |n=no |s=no |voy=no |species=no |v=Java |d=Q251}} | |||
There are several JSRs related to the Java Language and core API packages. | |||
{{wikiversity|Java Platform, Enterprise Edition/Java EE Tutorial}} | |||
* ''Add ] To The Java Programming Language'' (J2SE 5.0) | |||
* | |||
* ''A Simple Assertion Facility'' (J2SE 1.4) | |||
* ''Logging API Specification'' (J2SE 1.4) | |||
* ''] APIs for the Java Platform'' (J2SE 1.4) | |||
* ''J2SE Merlin Release Contents'' (J2SE 1.4) | |||
* ''Java Memory Model and Thread Specification Revision'' (J2SE 5.0) | |||
* ''Concurrency Utilities'' (J2SE 5.0) | |||
* '']'' (J2SE 5.0) | |||
* ''J2SE 5.0 (Tiger) Release Contents'' (J2SE 5.0) | |||
* ''Extending the Java Programming Language with Enumerations, Autoboxing, Enhanced for loops and Static Import'' (J2SE 5.0) | |||
* ''More New I/O APIs for the Java Platform ("NIO.2")'' (Java SE 7) | |||
* ''Unicode Supplementary Character Support'' (J2SE 5.0) – support for ] 3.1 | |||
* ''Java SE 6 ("Mustang") Release Contents'' (Java SE 6) | |||
* ''Java Language Specification'' (J2SE 5.0) | |||
{{Java (software platform)}} | |||
===Tutorials=== | |||
{{Sun Microsystems}} | |||
* David Flanagan, ''Java in a Nutshell, Third Edition''. O'Reilly & Associates, 1999. ISBN 1565924878 | |||
{{Oracle}} | |||
* , by Bruce Eckel | |||
{{Oracle FOSS}} | |||
* The well-known book of A.B. Downey as an HTMLHelp based eBook | |||
{{Programming languages}} | |||
* Online textbook by David J. Eck | |||
{{Authority control}} | |||
* Java version | |||
* Well over 100 Java tutorials covering every Java topic. | |||
===Resources=== | |||
* | |||
* A collection of Java books available for free download | |||
* ] () and related | |||
* | |||
* | |||
* | |||
* | |||
* | |||
* | |||
* | |||
* Portal of Java websites | |||
* Java code samples | |||
* Java community | |||
* | |||
===History=== | |||
* | |||
* | |||
* | |||
* | |||
* | |||
* | |||
===Alternatives=== | |||
* for ], includes ] plugin | |||
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Latest revision as of 01:51, 20 January 2025
Object-oriented programming language Not to be confused with Java (software platform), JavaScript, Java, or Javanese language. "Openframe" redirects here. For the ten-pin bowling term, see Open frame.
[REDACTED] | |
Paradigm | Multi-paradigm: generic, object-oriented (class-based), functional, imperative, reflective, concurrent |
---|---|
Designed by | James Gosling |
Developer | Oracle Corporation |
First appeared | May 23, 1995; 29 years ago (1995-05-23) |
Typing discipline | Static, strong, safe, nominative, manifest |
Memory management | Automatic garbage collection |
Filename extensions | .java, .class, .jar, .jmod, .war |
Website | |
Influenced by | |
CLU, Simula67, Lisp, Smalltalk, Ada 83, C++, C#, Eiffel, Mesa, Modula-3, Oberon, Objective-C, UCSD Pascal, Object Pascal | |
Influenced | |
Ada 2005, BeanShell, C#, Chapel, Clojure, ECMAScript, Fantom, Gambas, Groovy, Hack, Haxe, J#, Kotlin, PHP, Python, Scala, Seed7, Vala, JavaScript, JS++, ArkTS | |
|
Java is a high-level, class-based, object-oriented programming language that is designed to have as few implementation dependencies as possible. It is a general-purpose programming language intended to let programmers write once, run anywhere (WORA), meaning that compiled Java code can run on all platforms that support Java without the need to recompile. Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM) regardless of the underlying computer architecture. The syntax of Java is similar to C and C++, but has fewer low-level facilities than either of them. The Java runtime provides dynamic capabilities (such as reflection and runtime code modification) that are typically not available in traditional compiled languages.
Java gained popularity shortly after its release, and has been a popular programming language since then. Java was the third most popular programming language in 2022 according to GitHub. Although still widely popular, there has been a gradual decline in use of Java in recent years with other languages using JVM gaining popularity.
Java was designed by James Gosling at Sun Microsystems. It was released in May 1995 as a core component of Sun's Java platform. The original and reference implementation Java compilers, virtual machines, and class libraries were released by Sun under proprietary licenses. As of May 2007, in compliance with the specifications of the Java Community Process, Sun had relicensed most of its Java technologies under the GPL-2.0-only license. Oracle, which bought Sun in 2010, offers its own HotSpot Java Virtual Machine. However, the official reference implementation is the OpenJDK JVM, which is open-source software used by most developers and is the default JVM for almost all Linux distributions.
Java 23 is the version current as of September 2024. Java 20 and 22 are no longer maintained. Java 8, 11, 17, and 21 are long-term support versions still under maintenance.
History
See also: Java (software platform) § HistoryJames Gosling, Mike Sheridan, and Patrick Naughton initiated the Java language project in June 1991. Java was originally designed for interactive television, but it was too advanced for the digital cable television industry at the time. The language was initially called Oak after an oak tree that stood outside Gosling's office. Later the project went by the name Green and was finally renamed Java, from Java coffee, a type of coffee from Indonesia. Gosling designed Java with a C/C++-style syntax that system and application programmers would find familiar.
Sun Microsystems released the first public implementation as Java 1.0 in 1996. It promised write once, run anywhere (WORA) functionality, providing no-cost run-times on popular platforms. Fairly secure and featuring configurable security, it allowed network- and file-access restrictions. Major web browsers soon incorporated the ability to run Java applets within web pages, and Java quickly became popular. The Java 1.0 compiler was re-written in Java by Arthur van Hoff to comply strictly with the Java 1.0 language specification. With the advent of Java 2 (released initially as J2SE 1.2 in December 1998 – 1999), new versions had multiple configurations built for different types of platforms. J2EE included technologies and APIs for enterprise applications typically run in server environments, while J2ME featured APIs optimized for mobile applications. The desktop version was renamed J2SE. In 2006, for marketing purposes, Sun renamed new J2 versions as Java EE, Java ME, and Java SE, respectively.
In 1997, Sun Microsystems approached the ISO/IEC JTC 1 standards body and later the Ecma International to formalize Java, but it soon withdrew from the process. Java remains a de facto standard, controlled through the Java Community Process. At one time, Sun made most of its Java implementations available without charge, despite their proprietary software status. Sun generated revenue from Java through the selling of licenses for specialized products such as the Java Enterprise System.
On November 13, 2006, Sun released much of its Java virtual machine (JVM) as free and open-source software (FOSS), under the terms of the GPL-2.0-only license. On May 8, 2007, Sun finished the process, making all of its JVM's core code available under free software/open-source distribution terms, aside from a small portion of code to which Sun did not hold the copyright.
Sun's vice-president Rich Green said that Sun's ideal role with regard to Java was as an evangelist. Following Oracle Corporation's acquisition of Sun Microsystems in 2009–10, Oracle has described itself as the steward of Java technology with a relentless commitment to fostering a community of participation and transparency. This did not prevent Oracle from filing a lawsuit against Google shortly after that for using Java inside the Android SDK (see the Android section).
On April 2, 2010, James Gosling resigned from Oracle.
In January 2016, Oracle announced that Java run-time environments based on JDK 9 will discontinue the browser plugin.
Java software runs on everything from laptops to data centers, game consoles to scientific supercomputers.
Oracle (and others) highly recommend uninstalling outdated and unsupported versions of Java, due to unresolved security issues in older versions.
Principles
There were five primary goals in creating the Java language:
- It must be simple, object-oriented, and familiar.
- It must be robust and secure.
- It must be architecture-neutral and portable.
- It must execute with high performance.
- It must be interpreted, threaded, and dynamic.
Versions
Main article: Java version historyAs of November 2024, Java 8, 11, 17, and 21 are supported as long-term support (LTS) versions, with Java 25, releasing in September 2025, as the next scheduled LTS version.
Oracle released the last zero-cost public update for the legacy version Java 8 LTS in January 2019 for commercial use, although it will otherwise still support Java 8 with public updates for personal use indefinitely. Other vendors such as Adoptium continue to offer free builds of OpenJDK's long-term support (LTS) versions. These builds may include additional security patches and bug fixes.
Major release versions of Java, along with their release dates:
Version | Date |
---|---|
JDK Beta | 1995 |
JDK 1.0 | January 23, 1996 |
JDK 1.1 | February 19, 1997 |
J2SE 1.2 | December 8, 1998 |
J2SE 1.3 | May 8, 2000 |
J2SE 1.4 | February 6, 2002 |
J2SE 5.0 | September 30, 2004 |
Java SE 6 | December 11, 2006 |
Java SE 7 | July 28, 2011 |
Java SE 8 (LTS) | March 18, 2014 |
Java SE 9 | September 21, 2017 |
Java SE 10 | March 20, 2018 |
Java SE 11 (LTS) | September 25, 2018 |
Java SE 12 | March 19, 2019 |
Java SE 13 | September 17, 2019 |
Java SE 14 | March 17, 2020 |
Java SE 15 | September 15, 2020 |
Java SE 16 | March 16, 2021 |
Java SE 17 (LTS) | September 14, 2021 |
Java SE 18 | March 22, 2022 |
Java SE 19 | September 20, 2022 |
Java SE 20 | March 21, 2023 |
Java SE 21 (LTS) | September 19, 2023 |
Java SE 22 | March 19, 2024 |
Java SE 23 | September 17, 2024 |
Editions
See also: Free Java implementations § Class libraryJava platform editions |
---|
|
Sun has defined and supports four editions of Java targeting different application environments and segmented many of its APIs so that they belong to one of the platforms. The platforms are:
- Java Card for smart-cards.
- Java Platform, Micro Edition (Java ME) – targeting environments with limited resources.
- Java Platform, Standard Edition (Java SE) – targeting workstation environments.
- Java Platform, Enterprise Edition (Java EE) – targeting large distributed enterprise or Internet environments.
The classes in the Java APIs are organized into separate groups called packages. Each package contains a set of related interfaces, classes, subpackages and exceptions.
Sun also provided an edition called Personal Java that has been superseded by later, standards-based Java ME configuration-profile pairings.
Execution system
Java JVM and bytecode
Main articles: Java (software platform) and Java virtual machineOne design goal of Java is portability, which means that programs written for the Java platform must run similarly on any combination of hardware and operating system with adequate run time support. This is achieved by compiling the Java language code to an intermediate representation called Java bytecode, instead of directly to architecture-specific machine code. Java bytecode instructions are analogous to machine code, but they are intended to be executed by a virtual machine (VM) written specifically for the host hardware. End-users commonly use a Java Runtime Environment (JRE) installed on their device for standalone Java applications or a web browser for Java applets.
Standard libraries provide a generic way to access host-specific features such as graphics, threading, and networking.
The use of universal bytecode makes porting simple. However, the overhead of interpreting bytecode into machine instructions made interpreted programs almost always run more slowly than native executables. Just-in-time (JIT) compilers that compile byte-codes to machine code during runtime were introduced from an early stage. Java's Hotspot compiler is actually two compilers in one; and with GraalVM (included in e.g. Java 11, but removed as of Java 16) allowing tiered compilation. Java itself is platform-independent and is adapted to the particular platform it is to run on by a Java virtual machine (JVM), which translates the Java bytecode into the platform's machine language.
Performance
Main article: Java performancePrograms written in Java have a reputation for being slower and requiring more memory than those written in C++. However, Java programs' execution speed improved significantly with the introduction of just-in-time compilation in 1997/1998 for Java 1.1, the addition of language features supporting better code analysis (such as inner classes, the StringBuilder class, optional assertions, etc.), and optimizations in the Java virtual machine, such as HotSpot becoming Sun's default JVM in 2000. With Java 1.5, the performance was improved with the addition of the java.util.concurrent
package, including lock-free implementations of the ConcurrentMaps and other multi-core collections, and it was improved further with Java 1.6.
Non-JVM
Some platforms offer direct hardware support for Java; there are micro controllers that can run Java bytecode in hardware instead of a software Java virtual machine, and some ARM-based processors could have hardware support for executing Java bytecode through their Jazelle option, though support has mostly been dropped in current implementations of ARM.
Automatic memory management
Java uses an automatic garbage collector to manage memory in the object lifecycle. The programmer determines when objects are created, and the Java runtime is responsible for recovering the memory once objects are no longer in use. Once no references to an object remain, the unreachable memory becomes eligible to be freed automatically by the garbage collector. Something similar to a memory leak may still occur if a programmer's code holds a reference to an object that is no longer needed, typically when objects that are no longer needed are stored in containers that are still in use. If methods for a non-existent object are called, a null pointer exception is thrown.
One of the ideas behind Java's automatic memory management model is that programmers can be spared the burden of having to perform manual memory management. In some languages, memory for the creation of objects is implicitly allocated on the stack or explicitly allocated and deallocated from the heap. In the latter case, the responsibility of managing memory resides with the programmer. If the program does not deallocate an object, a memory leak occurs. If the program attempts to access or deallocate memory that has already been deallocated, the result is undefined and difficult to predict, and the program is likely to become unstable or crash. This can be partially remedied by the use of smart pointers, but these add overhead and complexity. Garbage collection does not prevent logical memory leaks, i.e. those where the memory is still referenced but never used.
Garbage collection may happen at any time. Ideally, it will occur when a program is idle. It is guaranteed to be triggered if there is insufficient free memory on the heap to allocate a new object; this can cause a program to stall momentarily. Explicit memory management is not possible in Java.
Java does not support C/C++ style pointer arithmetic, where object addresses can be arithmetically manipulated (e.g. by adding or subtracting an offset). This allows the garbage collector to relocate referenced objects and ensures type safety and security.
As in C++ and some other object-oriented languages, variables of Java's primitive data types are either stored directly in fields (for objects) or on the stack (for methods) rather than on the heap, as is commonly true for non-primitive data types (but see escape analysis). This was a conscious decision by Java's designers for performance reasons.
Java contains multiple types of garbage collectors. Since Java 9, HotSpot uses the Garbage First Garbage Collector (G1GC) as the default. However, there are also several other garbage collectors that can be used to manage the heap, such as the Z Garbage Collector (ZGC) introduced in Java 11, and Shenandoah GC, introduced in Java 12 but unavailable in Oracle-produced OpenJDK builds. Shenandoah is instead available in third-party builds of OpenJDK, such as Eclipse Temurin. For most applications in Java, G1GC is sufficient. In prior versions of Java, such as Java 8, the Parallel Garbage Collector was used as the default garbage collector.
Having solved the memory management problem does not relieve the programmer of the burden of handling properly other kinds of resources, like network or database connections, file handles, etc., especially in the presence of exceptions.
Syntax
Main article: Java syntaxThe syntax of Java is largely influenced by C++ and C. Unlike C++, which combines the syntax for structured, generic, and object-oriented programming, Java was built almost exclusively as an object-oriented language. All code is written inside classes, and every data item is an object, with the exception of the primitive data types, (i.e. integers, floating-point numbers, boolean values, and characters), which are not objects for performance reasons. Java reuses some popular aspects of C++ (such as the printf
method).
Unlike C++, Java does not support operator overloading or multiple inheritance for classes, though multiple inheritance is supported for interfaces.
Java uses comments similar to those of C++. There are three different styles of comments: a single line style marked with two slashes (//
), a multiple line style opened with /*
and closed with */
, and the Javadoc commenting style opened with /**
and closed with */
. The Javadoc style of commenting allows the user to run the Javadoc executable to create documentation for the program and can be read by some integrated development environments (IDEs) such as Eclipse to allow developers to access documentation within the IDE.
Hello world
The following is a simple example of a "Hello, World!" program that writes a message to the standard output:
public class Example { public static void main(String args) { System.out.println("Hello World!"); } }
Special classes
This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed. Find sources: "Java" programming language – news · newspapers · books · scholar · JSTOR (May 2019) (Learn how and when to remove this message) |
Applet
Main article: Java appletJava applets are programs embedded in other applications, mainly in web pages displayed in web browsers. The Java applet API was deprecated with the release of Java 9 in 2017.
Servlet
Main article: Java servletJava servlet technology provides Web developers with a simple, consistent mechanism for extending the functionality of a Web server and for accessing existing business systems. Servlets are server-side Java EE components that generate responses to requests from clients. Most of the time, this means generating HTML pages in response to HTTP requests, although there are a number of other standard servlet classes available, for example for WebSocket communication.
The Java servlet API has to some extent been superseded (but still used under the hood) by two standard Java technologies for web services:
- the Java API for RESTful Web Services (JAX-RS 2.0) useful for AJAX, JSON and REST services, and
- the Java API for XML Web Services (JAX-WS) useful for SOAP Web Services.
Typical implementations of these APIs on Application Servers or Servlet Containers use a standard servlet for handling all interactions with the HTTP requests and responses that delegate to the web service methods for the actual business logic.
JavaServer Pages
Main article: JavaServer PagesJavaServer Pages (JSP) are server-side Java EE components that generate responses, typically HTML pages, to HTTP requests from clients. JSPs embed Java code in an HTML page by using the special delimiters <%
and %>
. A JSP is compiled to a Java servlet, a Java application in its own right, the first time it is accessed. After that, the generated servlet creates the response.
Swing application
Main article: Swing (Java)Swing is a graphical user interface library for the Java SE platform. It is possible to specify a different look and feel through the pluggable look and feel system of Swing. Clones of Windows, GTK+, and Motif are supplied by Sun. Apple also provides an Aqua look and feel for macOS. Where prior implementations of these looks and feels may have been considered lacking, Swing in Java SE 6 addresses this problem by using more native GUI widget drawing routines of the underlying platforms.
JavaFX application
Main article: JavaFXJavaFX is a software platform for creating and delivering desktop applications, as well as rich web applications that can run across a wide variety of devices. JavaFX is intended to replace Swing as the standard graphical user interface (GUI) library for Java SE, but since JDK 11 JavaFX has not been in the core JDK and instead in a separate module. JavaFX has support for desktop computers and web browsers on Microsoft Windows, Linux, and macOS. JavaFX does not have support for native OS look and feels.
Generics
Main article: Generics in JavaIn 2004, generics were added to the Java language, as part of J2SE 5.0. Prior to the introduction of generics, each variable declaration had to be of a specific type. For container classes, for example, this is a problem because there is no easy way to create a container that accepts only specific types of objects. Either the container operates on all subtypes of a class or interface, usually Object
, or a different container class has to be created for each contained class. Generics allow compile-time type checking without having to create many container classes, each containing almost identical code. In addition to enabling more efficient code, certain runtime exceptions are prevented from occurring, by issuing compile-time errors. If Java prevented all runtime type errors (ClassCastException
s) from occurring, it would be type safe.
In 2016, the type system of Java was proven unsound in that it is possible to use generics to construct classes and methods that allow assignment of an instance of one class to a variable of another unrelated class. Such code is accepted by the compiler, but fails at run time with a class cast exception.
Criticism
Main article: Criticism of JavaCriticisms directed at Java include the implementation of generics, speed, the handling of unsigned numbers, the implementation of floating-point arithmetic, and a history of security vulnerabilities in the primary Java VM implementation HotSpot. Developers have criticized the complexity and verbosity of the Java Persistence API (JPA), a standard part of Java EE. This has led to increased adoption of higher-level abstractions like Spring Data JPA, which aims to simplify database operations and reduce boilerplate code. The growing popularity of such frameworks suggests limitations in the standard JPA implementation's ease-of-use for modern Java development.
Class libraries
Main article: Java Class LibraryThe Java Class Library is the standard library, developed to support application development in Java. It is controlled by Oracle in cooperation with others through the Java Community Process program. Companies or individuals participating in this process can influence the design and development of the APIs. This process has been a subject of controversy during the 2010s. The class library contains features such as:
- The core libraries, which include:
- Input/output (I/O or IO) and non-blocking I/O (NIO), or IO/NIO
- Networking (new user agent (HTTP client) since Java 11)
- Reflective programming (reflection)
- Concurrent computing (concurrency)
- Generics
- Scripting, Compiler
- Functional programming (Lambda, streaming)
- Collection libraries that implement data structures such as lists, dictionaries, trees, sets, queues and double-ended queue, or stacks
- XML Processing (Parsing, Transforming, Validating) libraries
- Security
- Internationalization and localization libraries
- The integration libraries, which allow the application writer to communicate with external systems. These libraries include:
- The Java Database Connectivity (JDBC) API for database access
- Java Naming and Directory Interface (JNDI) for lookup and discovery
- Java remote method invocation (RMI) and Common Object Request Broker Architecture (CORBA) for distributed application development
- Java Management Extensions (JMX) for managing and monitoring applications
- User interface libraries, which include:
- The (heavyweight, or native) Abstract Window Toolkit (AWT), which provides GUI components, the means for laying out those components and the means for handling events from those components
- The (lightweight) Swing libraries, which are built on AWT but provide (non-native) implementations of the AWT widgetry
- APIs for audio capture, processing, and playback
- JavaFX
- A platform dependent implementation of the Java virtual machine that is the means by which the bytecodes of the Java libraries and third-party applications are executed
- Plugins, which enable applets to be run in web browsers
- Java Web Start, which allows Java applications to be efficiently distributed to end users across the Internet
- Licensing and documentation
Documentation
Main article: JavadocJavadoc is a comprehensive documentation system, created by Sun Microsystems. It provides developers with an organized system for documenting their code. Javadoc comments have an extra asterisk at the beginning, i.e. the delimiters are /**
and */
, whereas the normal multi-line comments in Java are delimited by /*
and */
, and single-line comments start with //
.
Implementations
See also: Free Java implementations and List of Java compilersThis section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed. Find sources: "Java" programming language – news · newspapers · books · scholar · JSTOR (September 2023) (Learn how and when to remove this message) |
Oracle Corporation owns the official implementation of the Java SE platform, due to its acquisition of Sun Microsystems on January 27, 2010. This implementation is based on the original implementation of Java by Sun. The Oracle implementation is available for Windows, macOS, Linux, and Solaris. Because Java lacks any formal standardization recognized by Ecma International, ISO/IEC, ANSI, or other third-party standards organizations, the Oracle implementation is the de facto standard.
The Oracle implementation is packaged into two different distributions: The Java Runtime Environment (JRE) which contains the parts of the Java SE platform required to run Java programs and is intended for end users, and the Java Development Kit (JDK), which is intended for software developers and includes development tools such as the Java compiler, Javadoc, Jar, and a debugger. Oracle has also released GraalVM, a high performance Java dynamic compiler and interpreter.
OpenJDK is another Java SE implementation that is licensed under the GNU GPL. The implementation started when Sun began releasing the Java source code under the GPL. As of Java SE 7, OpenJDK is the official Java reference implementation.
The goal of Java is to make all implementations of Java compatible. Historically, Sun's trademark license for usage of the Java brand insists that all implementations be compatible. This resulted in a legal dispute with Microsoft after Sun claimed that the Microsoft implementation did not support Java remote method invocation (RMI) or Java Native Interface (JNI) and had added platform-specific features of their own. Sun sued in 1997, and, in 2001, won a settlement of US$20 million, as well as a court order enforcing the terms of the license from Sun. As a result, Microsoft no longer ships Java with Windows.
Platform-independent Java is essential to Java EE, and an even more rigorous validation is required to certify an implementation. This environment enables portable server-side applications.
Use outside the Java platform
The Java programming language requires the presence of a software platform in order for compiled programs to be executed.
Oracle supplies the Java platform for use with Java. The Android SDK is an alternative software platform, used primarily for developing Android applications with its own GUI system.
Android
The Java language is a key pillar in Android, an open source mobile operating system. Although Android, built on the Linux kernel, is written largely in C, the Android SDK uses the Java language as the basis for Android applications but does not use any of its standard GUI, SE, ME or other established Java standards. The bytecode language supported by the Android SDK is incompatible with Java bytecode and runs on its own virtual machine, optimized for low-memory devices such as smartphones and tablet computers. Depending on the Android version, the bytecode is either interpreted by the Dalvik virtual machine or compiled into native code by the Android Runtime.
Android does not provide the full Java SE standard library, although the Android SDK does include an independent implementation of a large subset of it. It supports Java 6 and some Java 7 features, offering an implementation compatible with the standard library (Apache Harmony).
Controversy
See also: Oracle America, Inc. v. Google, Inc.The use of Java-related technology in Android led to a legal dispute between Oracle and Google. On May 7, 2012, a San Francisco jury found that if APIs could be copyrighted, then Google had infringed Oracle's copyrights by the use of Java in Android devices. District Judge William Alsup ruled on May 31, 2012, that APIs cannot be copyrighted, but this was reversed by the United States Court of Appeals for the Federal Circuit in May 2014. On May 26, 2016, the district court decided in favor of Google, ruling the copyright infringement of the Java API in Android constitutes fair use. In March 2018, this ruling was overturned by the Appeals Court, which sent down the case of determining the damages to federal court in San Francisco. Google filed a petition for writ of certiorari with the Supreme Court of the United States in January 2019 to challenge the two rulings that were made by the Appeals Court in Oracle's favor. On April 5, 2021, the Court ruled 6–2 in Google's favor, that its use of Java APIs should be considered fair use. However, the court refused to rule on the copyrightability of APIs, choosing instead to determine their ruling by considering Java's API copyrightable "purely for argument's sake."
See also
- C#
- C++
- Dalvik, used in old Android versions, replaced by non-JIT Android Runtime
- Java Heterogeneous Distributed Computing
- List of Java APIs
- List of Java frameworks
- List of JVM languages
- List of Java virtual machines
- Comparison of C# and Java
- Comparison of Java and C++
- Comparison of programming languages
References
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The project went ahead under the name green and the language was based on an old model of UCSD Pascal, which makes it possible to generate interpretive code.
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