Editing Java applet (section)

{{Short description|Small application written in Java}}
{{Use dmy dates|date=June 2023}}
[[File:Java applet.png|thumb|A Java applet that was created as supplementary demonstration material for a scientific publication]]
[[File:OpenAstexViewer.jpg|thumb|A Java applet that uses 3D [[hardware acceleration]] to visualize 3D files in [[Protein Data Bank (file format)|.pdb format]] downloaded from a server<ref>{{cite web|url=http://openastexviewer.net/web/|title=The home site of the 3D protein viewer (Openastexviewer) under LGPL|access-date=21 September 2009|archive-url=https://web.archive.org/web/20090801135810/http://www.openastexviewer.net/web/|archive-date=1 August 2009|url-status=dead}}</ref>]]
[[File:Cardiac cells applet.png|thumb|120px|Using applet for nontrivial animation illustrating biophysical topic (randomly moving ions pass through voltage gates)<ref name='heart'>{{Cite web|url=http://thevirtualheart.org/CAPindex.html|title=Generation of an action potential in cardiac cells using interactive java applet. Excitable media. movies excitable media Fitzhug nagumo beeler reuter luo rudy model mathematical cell modeling|website=Thevirtualheart.org|access-date=22 March 2022}}</ref>]]
[[File:Mandelbrot java applet.png|thumb|Using a Java applet for computation{{snd}} intensive visualization of the [[Mandelbrot set]]<ref>{{cite web|url=http://math.uchicago.edu/~dannyc/fractals/simple.html|title=The home site of the Mandelbrot set applet under GPL|access-date=29 July 2013|archive-url=https://web.archive.org/web/20130508054436/http://math.uchicago.edu/~dannyc/fractals/simple.html|archive-date=8 May 2013|url-status=dead}}</ref>]]
[[File:ChessApplet.png|thumb|Applets' running speed is sufficient for making e.g. nontrivial computer games that play [[chess]].<ref>{{cite web|url=http://english.op.org/~peter/ChessApp/ |title=The home site of the chess applet under BSD |url-status=dead |archive-url=https://web.archive.org/web/20090907072956/http://english.op.org/~peter/ChessApp/ |archive-date= 7 September 2009 }}</ref>]]
[[File:NASA World Wind.jpg|thumb|NASA [[World Wind]] (open source) is a second generation applet<ref>{{Cite web |url=http://java.sun.com/developer/technicalArticles/javase/newapplets/ |title=Next Generation in Applet Java Plug-in Technology |access-date=25 September 2009 |archive-date=4 April 2009 |archive-url=https://web.archive.org/web/20090404094007/http://java.sun.com/developer/technicalArticles/javase/newapplets/ |url-status=dead }}</ref> that makes heavy use of [[OpenGL]] and on-demand data downloading to provide a detailed 3D map of the world.]]
[[File:Remoteconsoleapplet.png|thumb|Web [[out-of-band management|access]] to the server console at the hardware level with the help of a Java applet]]
[[File:FFT2DApplet.png|thumb|Demonstration of image processing using two dimensional [[Fourier transform]] ]]
'''Java applets''' are [[applet|small applications]] written in the [[Java (programming language)|Java]] programming language, or another [[programming language]] that [[Compiled language|compiles]] to [[Java bytecode]], and delivered to users in the form of Java [[bytecode]].

At the time of their introduction, the intended use was for the user to launch the applet from a [[web page]], and for the applet to then execute within a [[Java virtual machine]] (JVM) in a [[Process (computing)|process]] separate from the [[web browser]] itself. A Java applet could appear in a frame of the web page, a new application window, a program from [[Sun Microsystems|Sun]] called appletviewer,<ref>{{Cite web |title=appletviewer — Java SE 8 |url=https://docs.oracle.com/javase/8/docs/technotes/tools/windows/appletviewer.html |access-date=December 5, 2023 |publisher=Oracle}}</ref> or a stand-alone tool for testing applets.{{What?|date=December 2023|reason=A standalone tool like what?}}

Java applets were introduced in the first version of the Java language, which was released in 1995. Beginning in 2013, major web browsers began to phase out support for [[NPAPI#Support/deprecation|NPAPI]], the underlying technology applets used to run. with applets becoming completely unable to be run by 2015&ndash;2017. Java applets were [[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}}</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>

Java applets were usually written in Java, but other languages such as [[Jython]], [[JRuby]], [[Pascal (programming language)|Pascal]],<ref>{{Cite web|url=https://wiki.freepascal.org/FPC_JVM|title=FPC JVM – Free Pascal wiki|website=Wiki.freepascal.org|access-date=22 March 2022}}</ref> [[Scala (programming language)|Scala]], [[NetRexx]], or [[Eiffel (programming language)|Eiffel]] (via [[SmartEiffel]]) could be used as well.

Unlike early versions of JavaScript, Java applets had access to 3D [[hardware acceleration]], making them well-suited for non-trivial, computation-intensive visualizations. Since applets' introduction, JavaScript has gained support for hardware-accelerated graphics via [[canvas element|canvas]] technology (or specifically [[WebGL]] in the case of 3D graphics),<ref>{{cite web |url=https://developer.mozilla.org/en-US/docs/Web/HTML/Element/canvas#Browser_compatibility|title=canvas – HTML|publisher=Mozilla Developer Network|access-date=15 August 2015}}</ref><ref>{{cite web |url= https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API#Browser_compatibility|title=WebGL – Web API Interfaces|publisher=Mozilla Developer Network|access-date=15 August 2015}}</ref> as well as [[just-in-time compilation]].<ref>{{cite web|url=https://developers.google.com/v8/design?hl=en|title=Design Elements – Chrome V8|access-date=15 August 2015}}</ref>

Since Java bytecode is [[cross-platform]] (or platform independent), Java applets could be executed by [[client (computing)|client]]s for many platforms, including [[Microsoft Windows]], [[FreeBSD]], [[Unix]], [[macOS]] and [[Linux]]. They could not be run on mobile devices, which do not support running standard Oracle JVM bytecode. [[Android (operating system)|Android]] devices can run code written in Java compiled for the [[Android Runtime]].