Java Development Kit

Java Development Kit (JDK)

File:Java logo.svg
Developer(s)	Sun Microsystems (Owned by Oracle Corporation)
Stable release	6 Update 18 / January 13, 2010
Operating system	Cross-platform
Type	Software development kit
License	Sun License (most of it also under GPL)
Website	http://java.sun.com/javase/

The Java Development Kit (JDK) is a Sun Microsystems product aimed at Java developers. Since the introduction of Java, it has been by far the most widely used Java SDK. On 17 November 2006, Sun announced that it would be released under the GNU General Public License (GPL), thus making it free software. This happened in large part on 8 May 2007 and the source code was contributed to the OpenJDK.

JDK contents

The JDK has as its primary components a selection of programming tools, including:

• java – The loader for Java applications. This tool is an interpreter and can interpret the class files generated by the javac compiler. Now a single launcher is used for both development and deployment. The old deployment launcher, jre, no longer comes with Sun JDK.
• javac – The compiler, which converts source code into Java bytecode
• jar – The archiver, which packages related class libraries into a single JAR file. This tool also helps manage JAR files.
• javadoc – The documentation generator, which automatically generates documentation from source code comments
• jdb – The debugger
• jps – The process status tool, which displays process information for current Java processes
• javap – The class file disassembler
• appletviewer – This tool can be used to run and debug Java applets without a web browser.
• javah – The C header and stub generator, used to write native methods
• javaws – The Java Web Start launcher for JNLP applications
• extcheck – This utility can detect JAR-file conflicts.
• apt – The annotation-processing tool
• jhat – (Experimental) Java heap analysis tool
• jstack – (Experimental) This utility prints Java stack traces of Java threads.
• jstat – (Experimental) Java Virtual Machine statistics monitoring tool
• jstatd – (Experimental) jstat daemon
• jinfo – (Experimental) This utility gets configuration information from a running Java process or crash dump.
• jmap – (Experimental) This utility outputs the memory map for Java and can print shared object memory maps or heap memory details of a given process or core dump.
• idlj – The IDL-to-Java compiler. This utility generates Java bindings from a given IDL file.
• policytool – The policy creation and management tool, which can determine policy for a Java runtime, specifying which permissions are available for code from various sources
• VisualVM – visual tool integrating several commandline JDK tools and lightweight performance and memory profiling capabilities
• wsimport – Generates portable JAX-WS artifacts for invoking a web service.
• jrunscript – Java command line script shell.

The JDK also comes with a complete Java Runtime Environment, usually called a private runtime. It consists of a Java Virtual Machine and all of the class libraries present in the production environment, as well as additional libraries only useful to developers, such as the internationalization libraries and the IDL libraries.

Also included are a wide selection of example programs demonstrating the use of almost all portions of the Java API.

Ambiguity between a JDK and an SDK

The JDK forms an extended subset of a software development kit (SDK). In the descriptions which accompany their recent releases for Java SE, EE, and ME, Sun acknowledge that under their terminology, the JDK forms the subset of the SDK which is responsible for the writing and running of Java programs.^{[citation needed]} The remainder of the SDK is composed of extra software, such as Application Servers, Debuggers, and Documentation.

Other JDKs

There are other JDKs commonly available for a variety of platforms, some of which started from the Sun JDK source and some which did not. All of them adhere to the basic Java specifications, but they often differ in explicitly unspecified areas, such as garbage collection, compilation strategies, and optimization techniques. They include:

• IBM's J9 JDK, for AIX, Linux, MVS, OS/400, Pocket PC, z/OS [1]
• Oracle Corporation's JRockit JDK, for Windows, Linux and Solaris [2]
• Blackdown Java – The Blackdown Group's port of Sun's JDK for Linux
• Apple's Mac OS Runtime for Java JVM/JDK for Mac OS [3]

See also

• Classpath (Java)
• Java platform
• Java version history

External links

• Sun Java SE – Sun's current stable release (6).
• IBM Java technology JDK
• Oracle's JRockit JDK
• Open source JDK 7 project
• Open source JDK project
• Community support
• GNU Classpath – a Free software JDK alternative
• Apache Harmony – an Open source JDK alternative
• Javadoc Developer Kit (JDK) Search Engine
• Developer Support Services from Sun Microsystems