Editing Java (programming language) (section)

== Special classes ==
{{more citations needed|section|date=May 2019}}

=== Applet ===
{{Main|Java applet}}
Java applets were programs embedded in other applications, mainly in web pages displayed in web browsers. The Java applet API was deprecated with the release of Java&nbsp;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 ===
{{Main|Java servlet}}
[[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 [[server-side]] Java EE components that generate responses to requests from [[client (computing)|clients]]. Most of the time, this means generating [[HTML]] pages in response to [[Hypertext Transfer Protocol|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The Java servlet API has to some extent been superseded (but still used under the hood) by two standard Java technologies for web services: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 Service]]s.

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|JavaServer Pages}}
JavaServer Pages ([[Jakarta Server Pages|JSP]]) are [[server-side]] Java EE components that generate responses, typically [[HTML]] pages, to [[Hypertext Transfer Protocol|HTTP]] requests from [[client (computing)|clients]]. JSPs embed Java code in an HTML page by using the special [[delimiter]]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 ===
{{Main|Swing (Java)}}
[[Swing (Java)|Swing]] is a graphical user interface [[library (computing)|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 [[Microsoft Windows|Windows]], [[GTK+]], and [[Motif (software)|Motif]] are supplied by Sun. [[Apple Inc.|Apple]] also provides an [[Aqua (user interface)|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 [[Graphical control element|GUI widget]] 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 ===
{{Main|JavaFX}}
[[JavaFX]] is a [[Computing platform|software platform]] for creating and delivering [[Application software|desktop applications]], as well as [[rich web application]]s that can run across a wide variety of devices. JavaFX is intended to replace [[Swing (Java)|Swing]] as the standard [[graphical user interface]] (GUI) library for [[Java Platform, Standard Edition|Java SE]], 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 [[desktop computer]]s and [[web browser]]s on [[Microsoft Windows]], [[Linux]], and [[macOS]]. 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}}

In 2004, [[generic programming|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 <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 [[type safety|type safe]].

In 2016, the type system of Java was proven [[soundness|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.<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>