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[[File:Duke (Java mascot) waving.svg|thumb|Duke (Java mascot)]]
'''Java''' is the name of a [[programming language]] created by [[Sun Microsystems]]. This company was bought out by [[Oracle Corporation]], which continues to keep it up to date. It is designed to be platform-independent, which means that code written in Java can run on any device or operating system that has a Java Virtual Machine (JVM) installed. This makes Java a popular choice for developing cross-platform applications and games. Additionally, Java has a large and active community, and a wide range of libraries and frameworks available for use.<ref name=":0">{{Cite web|date=2023-01-15|title=20 Best Java Coding Websites in 2023 - codershot|url=https://codershot.com/20-best-java-coding-websites/|access-date=2023-01-21|language=en-US}}</ref> {{As of|2023|March}}, [[:en:Java version history|Java&nbsp;20]] is the latest version (will be supported until September 2023), while Java 17, 11 and 8 are the current [[:en:long-term support|long-term support]] (LTS) versions. Being an LTS version means that it will continue getting updates for multiple years. The next planned LTS version is Java 21 (LTS), planned for September 2023.<ref>{{Cite web|url=https://www.oracle.com/java/technologies/java-se-support-roadmap.html|title=Oracle Java SE Support Roadmap|date=2021-09-13|access-date=2022-03-05|website=Oracle|language=en-US}}</ref>

Being an open-source platform, Java isn't just supported by Oracle, e.g., Eclipse Adoptium also supports Java (JVM), to at least May 2026 for Java 8, and at least September 2027 for Java 17.

Java, which was called ''Oak'' when it was still being developed, is [[Object-oriented programming|object-oriented]], meaning it is based on [[Object (computer science)|objects]] that work together to make programs do their jobs. Java code looks similar to [[C (programming language)|C]], [[C++]], or [[C Sharp (programming language)|C#]], but code written in those languages will not work in Java in most cases without being changed.<ref>{{Cite news|url=https://www.upwork.com/hiring/development/java-vs-c-which-language-is-right-for-your-software-project/|title=Java vs. C++: Which Language Is Right For Your Software Project?|date=2016-12-21|work=Hiring {{!}} Upwork|access-date=2018-10-05|language=en-US}}</ref>

Java runs on many [[operating system]]s, including [[Android (operating system)|Android]], the world's most popular [[mobile operating system]]<ref>{{Cite news|url=https://www.androidauthority.com/develop-android-apps-languages-learn-391008/|title=I want to develop Android Apps — What languages should I learn?|date=2017-12-24|work=Android Authority|access-date=2018-10-05|language=en-US}}</ref> (while Java continues to be used on Android, even by its maker [[Google]], they no longer prefer Java; now [[Kotlin_(programming_language)|Kotlin]] is their preferred language, though it can also be used with all Java code). This makes Java [https://codershot.com/20-best-java-coding-websites/ platform independent]. It does this by making the Java [[compiler]] turn code into Java [[bytecode]] instead of [[machine code]]. This means that when the program is [[:en:execution (computing)|executed]], a [[Java Virtual Machine]] interprets (or just-in-time compiles) the bytecode.<ref>{{Cite news|url=https://www.geeksforgeeks.org/java-platform-independent/|title=How is Java platform independent? - GeeksforGeeks|date=2017-06-23|work=GeeksforGeeks|access-date=2018-10-05|language=en-US}}</ref>

Java is both a language, but it's also a platform, and a number of languages compile to the same bytecode meant for that JVM platform, and can then work alone (without Java, the language, or with it). Google, that previously recommended Java, now recommends [[Kotlin (programming language)|Kotlin language]] over Java for its Android platform, and it, like any JVM language, can also work with or without Java in all other contexts where Java alone would have been used.

;High-profile JVM languages

* Java, a [[:en:Type system#Static type checking|statically-typed]] [[object-oriented programming|object-oriented]] language
* [[:en:Apache Groovy|Groovy]], a [[:en:dynamic programming language|dynamic programming language]] (also with static typing) and [[scripting language]]<ref name="oracle_eightlanguages"/>
* [[Kotlin (programming language)|Kotlin]], a statically-typed language from [[:en:JetBrains|JetBrains]], the developers of [[:en:IntelliJ IDEA|IntelliJ IDEA]]<ref name="oracle_eightlanguages"/> and Google's preferred language for Android
* [[Scala (programming language)|Scala]], a statically-typed object-oriented and [[functional programming]] language<ref>{{cite web|url=http://blog.objectmentor.com/articles/2009/01/15/adopting-new-jvm-languages-in-the-enterprise |title=Adopting New JVM Languages in the Enterprise (Updated) |last=Wampler |first=Dean |publisher=objectmentor.com |date=15 January 2009 |access-date=18 June 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090522071822/http://blog.objectmentor.com/articles/2009/01/15/adopting-new-jvm-languages-in-the-enterprise |archive-date=22 May 2009}}</ref>
* [[:en:Clojure|Clojure]], a [[:en:dynamic programming language|dynamic]], and [[functional programming|functional]] [[:en:dialect (computing)|dialect]] of the [[Lisp (programming language)|Lisp]] [[programming language]]<ref name="oracle_eightlanguages">{{Cite web |url=https://www.oracle.com/technetwork/articles/java/architect-languages-2266279.html |title=Alternative Languages for the JVM. A look at eight features from eight JVM languages |last=Urma |first=Raoul-Gabriel |access-date=2019-03-13 |date=2014-07-01 |publisher=Oracle}}</ref> ([[:en:ClojureScript|ClojureScript]] is an implementation targeting the web with [[JavaScript]], not the JVM.)
== Java concepts ==
Java was developed to achieve five main goals. These are:<ref>James Gosling, Henry McGilton: [http://java.sun.com/docs/white/langenv/Intro.doc2.html ''The Java Language Environment. 1.2 Design Goals of the Java Programming Language.''] Mai 1996.</ref><ref>''[http://www.cs.dartmouth.edu/~mckeeman/cs118/references/OriginalJavaWhitepaper.pdf The Java Language: An Overview.]'' James Gosling, February 1995</ref><ref>{{Cite web|url=https://coderslegacy.com/understanding-bytecode-and-java-virtual-machines/|title=Understanding Bytecode and Java Virtual Machines|last=Shadow|date=2020-05-25|website=CodersLegacy|language=en-US|access-date=2020-05-29}}</ref>
* Java should be easy to learn, object-oriented, and distributed.
* Java should be safe and strong.
* Java should not depend on any [[computer architecture]] or platform.
* Java should function well.
* Java should be able to have an interpreter written for it (for better portability), support [[Parallel computing|parallelism]], and use dynamic typing.
== Java platform ==
The ''Java platform'' refers to a group of [[software]] products from [[Sun Microsystems]]. The platform is used to develop and run Java programs. The platform includes the execution engine (called a [[Java Virtual Machine]]) that allows Java programs to do the same thing on different computer systems.

This capability of being able to develop software on one platform and running it on other platforms is called "[[cross-platform]] capability".

There are many resources available for learning Java programming, including books, tutorials, and online courses.<ref name=":0" />
== Programming example ==
An example of a [[Hello world program|"Hello World"]] Java program:

<syntaxhighlight lang="java">
// This is a simple program in Java. It shows "Hello World!" on the screen. 
public class HelloWorld {
    public static void main(String[] args) {
         System.out.println("Hello World!"); 
    }
}
</syntaxhighlight>
== Types of Java programs ==
There are many types of Java programs which run differently:

* [[Java application]] – executes on a client computer.  If online, it has to be downloaded before being run.
** Java applications do not generally run on mobile platforms, but Android has historically also used Java, and Android apps written in Java, to run on Android still work; those applications do not work on other operating systems in general, unlike regular Java applications, and Google now recommends using the [[Kotlin (programming language)|Kotlin language]] over using Java to write such applications.
* [[JAR (file format)|JAR file]] (''Java archive'') – used to package Java files together into a single file (almost exactly like a [[Zip (file format)|.zip]] file).
* Servlet – runs on a [[server|web server]] and helps to generate web pages.
* Swing application – used to build an application that has a [[GUI]] (windows, buttons, menus, etc.).
* [[Enterprise Java Beans|EJB]] – runs on a web server and is used to develop large, complex websites.
* [[Applet|Java Applet]] – small program written in Java and that was automatically downloaded from a website and historically could be executed within a [[web browser]] on a client computer; such applets were introduced in 1995, could run in most web browers, but beginning in 2013, [[:en:NPAPI#Support/deprecation|major web browsers began to phase out support for the underlying technology applets used to run]], with applets becoming completely unable to be run by 2015&ndash;2017. Java applets were [[:en:deprecation|deprecated]] by Java 9 in 2017.<ref>{{cite web|url=http://www.oracle.com/technetwork/java/javase/9-deprecated-features-3745636.html|title=Java 9 Release Notes|website=Oracle.com}}</ref><ref>{{Cite web|url=http://openjdk.java.net/jeps/289|title=JEP 289: Deprecate the Applet API|website=Openjdk.java.net|access-date=22 March 2022}}</ref><ref>{{cite web|url=https://blogs.oracle.com/java-platform-group/entry/moving_to_a_plugin_free|title=JPG blog: Moving to a Plugin-Free Web|website=Blogs.oracle.com|access-date=2023-07-03|archive-date=2016-03-16|archive-url=https://web.archive.org/web/20160316164325/https://blogs.oracle.com/java-platform-group/entry/moving_to_a_plugin_free|url-status=dead}}</ref><ref>{{cite web|url=https://blogs.oracle.com/java-platform-group/entry/further_updates_to_moving_to|title=JPG blog: Further Updates to 'Moving to a Plugin-Free Web'|website=Blogs.oracle.com}}</ref><ref>{{cite web|url=http://www.oracle.com/technetwork/java/javase/javaclientroadmapupdate2018mar-4414431.pdf|title=Java Client Roadmap Update|website=Oracle.com|access-date=22 March 2022}}</ref>
== Benefits ==
Java is commonly used to teach students how to program as a first language, but is still also used by professionals.

* Java requires that each variable be initialized.  Some older languages, such as C, allow variables to go uninitialized, which can cause random failures with mysterious bugs.
* Java requires that each [[Method (computer science)|method]] declares a return type—the method should always return a value, except if its return type is ''void''. This also prevents bugs.
* Java comes with a large set of classes and methods, the Java [[API]] that can be used without having to develop as much code "from scratch".
* Unlike C, Java primitive types, such as int, are always the same size in the number of bits, which helps achieve cross-platform compatibility.
* Java used to be thought of as being slower than C, but that's become less important in recent years because computers are faster.
* Java has exception-handling that requires a programmer to handle error-conditions such as Input/Output errors.
* Code compiled on one Java platform can be run on other platforms that support Java without modification of either the source-code nor the byte-code.  This means that a person can make a Java program for a Windows computer and have it run on a [[Linux]] computer or a Mac computer.
== Criticism ==
Java has also been criticized. Some criticisms are:

* [[:en:Generics_in_Java|Generics]] were added to Java in such a way so that existing code would still keep running. This was done using [[:en:type erasure|type erasure]]. This means that during compilation, the actual type of a generic argument is removed. This can lead to the Java interpreter to behave in unexpected ways at times.
* Java has no unsigned [[integer]] types, which languages like C heavily use. This also means that it is impossible to directly exchange numeric data between C and Java programs. [[Cryptography]] also relies on such types to some extent; this makes it more difficult to write applications that use cryptography in Java.
* The [[IEEE]] has defined a standard for floating-point arithmetic, [[:en:IEEE 754-2008 revision|IEEE 754]]. Java only supports a part of the features of this standard.

== Java (programming Language) Media ==
<gallery widths='160px' heights='100%' mode='traditional' caption=''>
File:James Gosling 2008.jpg|[[James Gosling]], the creator of Java, in 2008

File:JavaUniverse.png|This dependency graph of the Java Core classes was created with jdeps and [[Gephi]].
</gallery>
== References ==
{{reflist}}
== Other websites ==
* [http://www.java.com/ Java home page]

[[Category:Object-oriented programming languages|Java]]
[[Category:Sun Microsystems]]
[[Category:Oracle Corporation]]
[[Category:Cross-platform software]]
[[Category:Java (programming language)]]