129.97.124.58: /* Implementation and configuration */

2025-04-01T18:56:16Z

Implementation and configuration

New page

{{Short description|Core Java libraries}}
{{more citations needed|date=August 2011}}
The '''Java Class Library''' ('''JCL''') is a set of [[Library (computer science)#Dynamic linking|dynamically loadable libraries]] that [[List of JVM languages|Java Virtual Machine (JVM) languages]] can call at [[Run time (program lifecycle phase)|run time]]. Because the [[Java Platform]] is not dependent on a specific [[operating system]], applications cannot rely on any of the platform-native libraries. Instead, the Java Platform provides a comprehensive set of [[Standard library|standard class libraries]], containing the functions common to modern operating systems.

JCL serves three purposes within the JVM:
* Like other [[Standard library|standard code libraries]], they provide the programmer a well-known set of useful facilities, such as [[Collection class|container classes]] and [[regular expression]] processing.
* The library provides an abstract interface to tasks that would normally depend heavily on the hardware and operating system, such as [[Computer networking|network]] access and [[Computer file|file]] access.
* Some underlying platforms may not support all of the features a Java application expects. In these cases, the library implementation can either emulate those features or provide a consistent way to check for the presence of a specific feature.

==Implementation and configuration==
JCL is almost entirely written in Java, except for the parts that need direct access to the [[Computer hardware|hardware]] and [[operating system]] (such as for [[Input/output|I/O]] or [[Rasterisation|bitmap graphics]]), which are instead written in [[C++]].<ref>{{cite web|url=https://github.com/openjdk/jdk|title=Based on the OpenJDK sources|access-date=23 October 2021|publisher=[[OpenJDK]]}}</ref> The classes that give access to these functions commonly use [[Java Native Interface]] wrappers to access operating system [[API]]s.

Almost all of JCL is stored in a single [[JAR (file format)|Java archive]] file called "rt.jar" which is provided with [[Java Runtime Environment|JRE]] and [[Java Development Kit|JDK]] distributions. The Java Class Library (rt.jar) is located in the default bootstrap classpath<ref>{{cite web | url=http://java.sun.com/javase/6/docs/technotes/tools/findingclasses.html | title=How Classes are Found | publisher=[[Oracle Corporation]] | accessdate=2015-12-05 | archive-date=2009-04-25 | archive-url=https://web.archive.org/web/20090425152829/http://java.sun.com/javase/6/docs/technotes/tools/findingclasses.html | url-status=live }}</ref> and does not have to appear in the [[Classpath (Java)|classpath]] declared for the application. The [[Java Runtime Environment|runtime]] uses the bootstrap class loader to find the JCL.

The [[Java Module System]] (part of the [[Java 9]] release) broke the monolithic "rt.jar" JAR file and modularized the JCL itself in several modules with specified dependencies.<ref>{{cite web | url=http://cr.openjdk.java.net/~mr/jigsaw/ea/module-summary.html | title=JDK Module Summary | publisher=[[Oracle Corporation]] | date=2015-10-23 | accessdate=2015-11-29 | archive-date=2015-12-08 | archive-url=https://web.archive.org/web/20151208074800/http://cr.openjdk.java.net/~mr/jigsaw/ea/module-summary.html | url-status=dead}}</ref>

==Conformance==
Any Java implementation must pass the Java [[Technology Compatibility Kit]] tests for compliance, which includes JCL tests.

==Main features==
{{Main|Java Platform, Standard Edition}}
JCL Features are accessed through [[Class (computer science)|classes]] provided in [[Java package|packages]].
* {{Javadoc:SE|package=java.lang|java/lang}} contains fundamental classes and [[interface (Java)|interfaces]] closely tied to the language and [[Java Runtime Environment|runtime system]].
* [[Input/output|I/O]] and [[Computer networking|networking]] access the platform [[file system]], and more generally [[Computer network|networks]] through the {{Javadoc:SE|package=java.io|java/io}}, {{Javadoc:SE|package=java.nio|java/nio}} and {{Javadoc:SE|package=java.net|java/net}} packages. For networking, [[SCTP]] is available through {{Javadoc:SE|package=com.sun.nio.sctp|com/sun/nio/sctp|module=jdk.sctp}}.
* [[java.math|Mathematics package]]: {{Javadoc:SE|package=java.math|java/math}} provides mathematical expressions and evaluation, as well as arbitrary-precision decimal and integer number datatypes.
* [[Collection class|Collections]] and Utilities : built-in Collection [[data structure]]s, and utility classes, for [[regular expression]]s, [[Concurrent computing|concurrency]], [[Computer data logging|logging]] and [[data compression]].
* [[GUI]] and [[2D computer graphics|2D Graphics]]: the [[Abstract Window Toolkit|AWT]] package ({{Javadoc:SE|package=java.awt|java/awt|module=java.desktop}}) basic GUI operations and binds to the underlying native system. It also contains the 2D Graphics API. The [[Swing (java)|Swing]] package ({{Javadoc:SE|package=javax.swing|javax/swing|module=java.desktop}}) is built on AWT and provides a platform-independent [[widget toolkit]], as well as a [[pluggable look and feel]]. It also deals with editable and non-editable text components.
* Sound: interfaces and classes for reading, writing, [[Music sequencer|sequencing]], and [[Synthesizer|synthesizing]] of sound data.
* Text: {{Javadoc:SE|package=java.text|java/text}} deals with text, dates, numbers and messages.
* Image package: {{Javadoc:SE|package=java.awt.image|java/awt/image|module=java.desktop}} and {{Javadoc:SE|package=javax.imageio|javax/imageio|module=java.desktop}} provide APIs to write, read, and modify images.
* [[XML]]: [[Simple API for XML|SAX]], [[Document Object Model|DOM]], [[StAX]], [[XSL Transformations|XSLT transforms]], [[XPath]] and various APIs for [[Web service]]s, as [[SOAP|SOAP protocol]] and [[Java API for XML Web Services|JAX-WS]].
* Security is provided by {{Javadoc:SE|package=java.security|java/security}} and encryption services are provided by {{Javadoc:SE|package=javax.crypto|javax/crypto}}.
* [[Database]]s: access to [[SQL]] databases via {{Javadoc:SE|package=java.sql|java/sql|module=java.sql}}
* Access to Scripting engines: The {{Javadoc:SE|package=javax.script|javax/script|module=java.scripting}} package gives access to any conforming [[Scripting language]].
* [[Java applet|Applets]]: {{Javadoc:SE|package=java.applet|java/applet|module=java.desktop}} allows applications to be downloaded over a network and run within a guarded sandbox
* [[JavaBean|Java Beans]]: {{Javadoc:SE|package=java.beans|java/beans|module=java.desktop}} provides ways to manipulate reusable components.
* Introspection and reflection: [http://docs.oracle.com/javase/7/docs/api/java/lang/Class.html java.lang.Class] represents a class, but other classes such as Method and Constructor are available in {{Javadoc:SE|package=java.lang.reflect|java/lang/reflect}}.

==Licensing==
{{See also|Free Java implementations|OpenJDK}}

===Prior licenses===
Before the release of OpenJDK, the [[Java Development Kit|JDK]] was based on a [[Proprietary software|proprietary license]].

Following their promise to release a fully buildable [[Java Development Kit|JDK]] based on almost completely free and open-source code in the first half of 2007,<ref>{{Cite web |date=May 2007 |title=Free and Open Source Java - FAQ |url=http://www.sun.com/software/opensource/java/faq.jsp#b4 |url-status=dead |archive-url=https://web.archive.org/web/20070522170749/http://www.sun.com/software/opensource/java/faq.jsp#b4 |archive-date=May 22, 2007 |access-date=2024-06-27 |website=sun.com |language=en}}</ref> Sun released the complete [[source code]] of the Class Library under the [[GPL]] on May 8, 2007, except some limited parts that were licensed by Sun from third parties who did not want their code to be released under an open-source license.<ref>{{cite web | url=http://mail.openjdk.java.net/pipermail/announce/2007-May.txt | title=Open JDK is here! | author=Rich Green | publisher=[[Sun Microsystems]] | date=2007-05-08 | accessdate=2011-11-25 | archive-date=2012-02-07 | archive-url=https://web.archive.org/web/20120207052347/http://mail.openjdk.java.net/pipermail/announce/2007-May.txt | url-status=live }}</ref> Sun's goal was to replace the parts that remain proprietary and closed source with alternative implementations and make the Class Library completely free and open source.

Until December 2010, the remaining encumbered part of the JDK was made available by [[Sun Microsystems|Sun]] then [[Oracle Corporation|Oracle]] as ''Binary Plugs''<ref>{{cite web | url=http://openjdk.java.net/legal/binary-plugs-2007-05-08.html | title=OpenJDK Binary Plugs | publisher=[[Sun Microsystems]] | date=2007-05-08 | accessdate=2011-11-25 | archive-url=https://web.archive.org/web/20120826021741/http://openjdk.java.net/legal/binary-plugs-2007-05-08.html | archive-date=2012-08-26 | url-status=dead}}</ref> which were required to build the JDK but not necessary to run it. {{As of|lc=y|2007|05}}, the only part of the Class library that remained proprietary and closed-source (4% {{as of|lc=y|2007|05}} for OpenJDK 7,<ref>{{cite web | url=http://fitzsim.org/blog/?p=17 | title=Plans for OpenJDK | last=Fitzsimmons|first=Thomas | date=2007-05-18 | accessdate=2007-05-22}}</ref> and less than 1% {{as of|lc=y|2008|05}} and OpenJDK 6<ref>{{cite web |url = http://langel.wordpress.com/2008/03/13/openjdk-in-fedora-9/ |title = OpenJDK to replace IcedTea in Fedora 9 |last = Angel |first = Lillian |date = 2008-03-13 |accessdate = 2008-04-05 |url-status = dead |archiveurl = https://archive.today/20121210052442/http://langel.wordpress.com/2008/03/13/openjdk-in-fedora-9/ |archivedate = 2012-12-10}}</ref><ref>{{cite web | url=http://developer.redhatmagazine.com/2008/03/12/openjdk-to-replace-icedtea-in-fedora-9/ | title=OpenJDK in Fedora 9! | last=Wade | first=Karsten | publisher=redhatmagazine.com | quote=''Thomas Fitzsimmons updated the Fedora 9 release notes source pages to reflect that Fedora 9 would ship with OpenJDK 6 instead of the IcedTea implementation of OpenJDK 7. Fedora 9 (Sulphur) is due to release in May 2008.'' | date=2008-03-13 | accessdate=2008-04-05 | archive-url=https://web.archive.org/web/20080421100346/http://developer.redhatmagazine.com/2008/03/12/openjdk-to-replace-icedtea-in-fedora-9/ | archive-date=2008-04-21 | url-status=dead}}</ref>) was<ref>{{cite web |url = http://weblogs.java.net/blog/robogeek/archive/2007/10/openjdk_encumbr.html |title = Plans for OpenJDK |last = Herron |first = David |date = 2007-10-04 |accessdate = 2007-10-09 |url-status = dead |archiveurl = https://web.archive.org/web/20071011014156/http://weblogs.java.net/blog/robogeek/archive/2007/10/openjdk_encumbr.html |archivedate = 2007-10-11}}</ref> the [[Simple Network Management Protocol|SNMP]] implementation.<ref name="openjdkb10">{{cite web |url=http://mail.openjdk.java.net/pipermail/jdk6-dev/2008-May/000058.html |title=OpenJDK 6 b10 source posted |date=2008-05-30 |accessdate=2008-06-01 |archive-date=2009-06-18 |archive-url=https://web.archive.org/web/20090618054843/http://mail.openjdk.java.net/pipermail/jdk6-dev/2008-May/000058.html |url-status=live }}</ref>

Since the first May 2007 release, Sun, with the help of the community, released as open-source or replaced with open-source alternatives almost all the encumbered code:
* All the audio engine code, including the [[Musical Instrument Digital Interface|software synthesizer]], became open source.<ref name="openjdkb10" /><ref>{{Cite web |url=http://openjdk.java.net/projects/audio-engine/ |title=audio-engine project page |access-date=2007-05-19 |archive-date=2007-05-16 |archive-url=https://web.archive.org/web/20070516132340/http://openjdk.java.net/projects/audio-engine/ |url-status=live }}</ref> The closed-source software synthesizer has been replaced by a new synthesizer developed specifically for OpenJDK called ''Gervill'',<ref>{{cite web |url = https://gervill.dev.java.net/ |archive-url = https://archive.today/20111004052704/https://gervill.dev.java.net/ |url-status = dead |archive-date = 2011-10-04 |title = Gervill – Software Synthesizer |accessdate = 2008-06-01}}</ref>
* All [[cryptography]] classes were released as open-source,<ref>{{cite web |url=http://mail.openjdk.java.net/pipermail/security-dev/2007-September/000015.html |title=Crypto has been added to OpenJDK |date=2007-09-27 |accessdate=2007-10-07 |archive-date=2007-12-25 |archive-url=https://web.archive.org/web/20071225035137/http://mail.openjdk.java.net/pipermail/security-dev/2007-September/000015.html |url-status=live }}</ref>
* The code that scales and [[Rasterisation|rasterizes]] [[Computer font|fonts]] uses open source [[FreeType]]<ref>{{Cite web |url=http://openjdk.java.net/projects/font-scaler/ |title=font-scaler projectpage |access-date=2007-05-19 |archive-date=2015-06-10 |archive-url=https://web.archive.org/web/20150610021721/http://openjdk.java.net/projects/font-scaler/ |url-status=live }}</ref><ref name="2dproject">{{Cite web |url=http://openjdk.java.net/groups/2d/ |title=Java2D project page |access-date=2007-05-19 |archive-date=2007-05-16 |archive-url=https://web.archive.org/web/20070516132229/http://openjdk.java.net/groups/2d/ |url-status=live }}</ref><ref>{{cite web |url=http://mail.openjdk.java.net/pipermail/font-scaler-dev/2007-August/000011.html |title=Freetype font rasteriser |date=2007-08-07 |accessdate=2007-11-24 |archive-date=2009-01-07 |archive-url=https://web.archive.org/web/20090107195849/http://mail.openjdk.java.net/pipermail/font-scaler-dev/2007-August/000011.html |url-status=live }}</ref>
* The native [[color management]] uses open-source [[LittleCMS]].<ref name="2dproject" /> There is a pluggable layer in the JDK, so that the commercial release of Java can use the original, proprietary color management system and OpenJDK can use LittleCMS.
* The [[Spatial anti-aliasing|anti-aliasing]] graphics [[Rasterisation|rasterizer]] code uses the open source Pisces renderer used in the [[phoneME]] project.<ref name="2dproject" /><ref>{{cite web|url=https://phoneme.dev.java.net/ phoneme.dev.java.net/ |title=Welcome to the PhoneME project |archive-url=https://web.archive.org/web/20070610234355/https://phoneme.dev.java.net/ |archive-date=2007-06-10}}</ref><ref>{{Cite web |url=http://openjdk.java.net/projects/graphics-rasterizer/ |title=graphics-rasterizer project page |access-date=2007-05-19 |archive-date=2007-05-16 |archive-url=https://web.archive.org/web/20070516132602/http://openjdk.java.net/projects/graphics-rasterizer/ |url-status=live }}</ref>
* The [[JavaScript]] plugin is open source (the [[Rhino (JavaScript engine)|JavaScript engine]] itself was open source from the beginning).<ref>{{cite web | url=http://icedtea.classpath.org/bugzilla/show_bug.cgi?id=85 | title=Javascript is encumbered and there is no javascript plugin support. | publisher=[[IcedTea]] | quote=''Changing Summary. JavaScript is no longer encumbered, but we still need liveconnect support.'' | date=2008-03-11 | accessdate=2008-06-01 | archive-date=2008-09-27 | archive-url=https://web.archive.org/web/20080927185957/http://icedtea.classpath.org/bugzilla/show_bug.cgi?id=85 | url-status=dead}}</ref>

===Open source release===
Beginning in December 2010, all the so-called ''binary plugs'' were replaced by [[Open-source model|open source]] replacements, making the entire JDK open.<ref>{{cite web | url=http://mail.openjdk.java.net/pipermail/build-dev/2010-December/003881.html | title=OpenJDK7 and OpenJDK6 Binary Plugs Logic Removed | author=Kelly O'Hair | publisher=[[Oracle Corporation]] | date=December 2010 | accessdate=2011-11-25 | archive-date=2022-04-07 | archive-url=https://web.archive.org/web/20220407115622/http://mail.openjdk.java.net/pipermail/build-dev/2010-December/003881.html | url-status=live }}</ref>

==Alternative implementations==
[[GNU Classpath]] is the other main free software class library for Java. Contrary to other implementations, it only implements the Class Library, and is used by many [[Free Java implementations|free Java runtimes]] (like [[Kaffe]], [[SableVM]], [[JamVM]]).

[[Apache Harmony]] was another free software class library. Its aim was to implement the other parts of the Java stack ([[Java virtual machine|Virtual Machine]], [[Java compiler|Compiler]], and other tools required for any [[Free Java implementations|Java implementation]]).

==See also==
{{Portal|Computer programming}}
* [[Java Platform, Standard Edition]]
* [[List of Java APIs]]
* [[OpenJDK]]
* [[Free Java implementations]]
* [[Standard library]]
* [[Java applet]]

==References==
{{reflist|1=2}}

==External links==
* [http://java.sun.com/j2se/ Java SE Main page]
* {{Javadoc:SE}}
* [http://java.sun.com/reference/api/index.html Java SE API documentation]
* Java software development kits (status {{As of|2006|alt=as of August 2006}}):
** [https://web.archive.org/web/20070610111552/https://jdk7.dev.java.net/ 1.7] (early development)
** [http://java.sun.com/javase/6/ 1.6] (stable, current)
** [http://java.sun.com/j2se/1.5.0/ 1.5] (stable)
** [http://java.sun.com/j2se/1.4.2/ 1.4] (stable)
** [http://java.sun.com/j2se/1.3/ 1.3] (obsolete)

{{Java (Sun)}}
{{Sun Microsystems}}

[[Category:Java (programming language)]]
[[Category:Java (programming language) libraries]]

Java Class Library - Revision history

129.97.124.58: /* Implementation and configuration */