posted Aug 13, 2009, 2:43 AM by Thiyagaraaj M [ updated Aug 16, 2009, 9:44 PM ]
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.
The primary components of the JDK are 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, is no longer provided 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
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
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
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 that will be 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..
The JDK is a subset of what is loosely defined as a software development kit (SDK) in the general sense. 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. The remainder of the SDK is composed of extra software, such as Application Servers, Debuggers, and Documentation.
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 areas that are explicitly unspecified, such as garbage collection, compilation strategies, and optimization techniques. They include: