The Java Class Library (JCL) is a set of dynamically loadable libraries that Java Virtual Machine (JVM) languages can call at run time. It is the standard library of Java and other JVM languages, and is thus sometimes called the Java Standard Library. 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 class libraries, containing the functions common to modern operating systems. Since Java 9, the Java Class Library can be accessed through module path using the Java Platform Module System.
JCL serves three purposes within the JVM:
- Like other standard code libraries, they provide the programmer a well-known set of useful facilities, such as 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 network access and 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.
It uses the namespaces java.*, javax.*, and jdk.*. Some bundled classes may reside in namespaces like sun.* or com.sun.* (for Sun Microsystems), but they are not considered part of the standard library. The javax namespace was primarily associated with Java Platform, Enterprise Edition as extension packages to the Java standard library.
rt.jar" JAR file and modularized the JCL itself in several modules with specified dependencies.Conformance
editAny Java implementation must pass the Java Technology Compatibility Kit tests for compliance, which includes JCL tests.
Main features
editJCL Features are accessed through classes provided in packages.
- java.nio and java.math provides mathematical expressions and evaluation, as well as arbitrary-precision decimal and integer number datatypes.
- Collections and Utilities : built-in Collection data structures, and utility classes, for regular expressions, concurrency, logging and data compression.
- GUI and 2D Graphics: the AWT package (java.text deals with text, dates, numbers and messages.
- Image package: java.security and encryption services are provided by javax.script package gives access to any conforming Scripting language.
- Applets: java.lang.Class represents a class, but other classes such as Method and Constructor are available in
Prior licenses
editBefore the release of OpenJDK, the JDK was based on a proprietary license.
Following their promise to release a fully buildable JDK based on almost completely free and open-source code in the first half of 2007, 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. 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 then Oracle as Binary Plugs which were required to build the JDK but not necessary to run it. as of May 2008 and OpenJDK 6) was the SNMP implementation.
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 software synthesizer, became open source. The closed-source software synthesizer has been replaced by a new synthesizer developed specifically for OpenJDK called Gervill.
- All cryptography classes were released as open-source.
- The code that scales and rasterizes fonts uses open source FreeType.
- The native color management uses open-source LittleCMS. 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 anti-aliasing graphics rasterizer code uses the open source Pisces renderer used in the phoneME project.
- The JavaScript plugin is open source (the JavaScript engine itself was open source from the beginning).
Open source release
editBeginning in December 2010, all the so-called binary plugs were replaced by open source replacements, making the entire JDK open.
Alternative implementations
editGNU 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 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 (Virtual Machine, Compiler, and other tools required for any Java implementation).
See also
edit- Java Platform, Standard Edition
- List of Java APIs
- OpenJDK
- Free Java implementations
- Standard library
- Java applet
References
edit- ↑ "netspace.javascript (Java SE 25 & JDK 25)". docs.oracle.com. Oracle Corporation. Retrieved 10 October 2025.
- ↑ "org.w3c.dom (Java SE 25 & JDK 25)". docs.oracle.com. Oracle Corporation. Retrieved 10 October 2025.
- ↑ Oracle Corporation. "FAQ - Sun Packages: Why Developers Should Not Write Programs That Call 'sun' Packages". oracle.com. Oracle Corporation. Retrieved 22 April 2026.
- ↑ Rich Green (2007-05-08). "Open JDK is here!". Sun Microsystems. Archived from the original on 2012-02-07. Retrieved 2011-11-25.
- ↑ Angel, Lillian (2008-03-13). "OpenJDK to replace IcedTea in Fedora 9". Retrieved 2008-04-05.{{cite web}}: CS1 maint: deprecated archival service (link)
- ↑ "OpenJDK 6 b10 source posted". 2008-05-30. Archived from the original on 2009-06-18. Retrieved 2008-06-01.
- ↑ "Crypto has been added to OpenJDK". 2007-09-27. Archived from the original on 2007-12-25. Retrieved 2007-10-07.
- ↑ "Freetype font rasteriser". 2007-08-07. Archived from the original on 2009-01-07. Retrieved 2007-11-24.
- ↑ "Javascript is encumbered and there is no javascript plugin support". IcedTea. 2008-03-11. Archived from the original on 2008-09-27. Retrieved 2008-06-01. Changing Summary. JavaScript is no longer encumbered, but we still need liveconnect support.
- ↑ Kelly O'Hair (December 2010). "OpenJDK7 and OpenJDK6 Binary Plugs Logic Removed". Oracle Corporation. Archived from the original on 2022-04-07. Retrieved 2011-11-25.
External links
edit- Java SE Main page
- Java SE 24 API Javadocs
- Java SE API documentation
- Java software development kits (status
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