The Java Development Kit is a development environment for building applications, components and applets using the Java programming language. 
The JDK includes tools useful for developing and testing programs written in the Java programming language and running on the Java platform.
Contents of the JDK
Development Tools
(In the bin/ subdirectory) Tools and utilities that will help you develop, execute, debug, and document programs written in the JavaTM programming language. 
Runtime Environment
(In the jre/ subdirectory) An implementation of the Java Runtime Environment (JRE) for use by the JDK. The JRE includes a Java Virtual Machine (JVM), class libraries, and other files that support the execution of programs written in the Java programming language.
Additional Libraries
(In the lib/ subdirectory) Additional class libraries and support files required by the development tools.
Demo Applets and Applications
(In the demo/ subdirectory) Examples, with source code, of programming for the Javaplatform. These include examples that use Swing and other Java Foundation Classes, and the Java Platform Debugger Architecture.
Sample Code
(In the sample subdirectory) Samples, with source code, of programming for certain Java API's.
C header Files
(In the include/ subdirectory) Header files that support native-code programming using the Java Native Interface, the JVM Tool Interface, and other functionality of the Javaplatform.
Source Code
(In src.zip) Java programming language source files for all classes that make up the Java core API (that is, sources files for the java.*, javax.* and some org.* packages, but not for com.sun.* packages). This source code is provided for informational purposes only, to help developers learn and use the Java programming language. These files do not include platform-specific implementation code and cannot be used to rebuild the class libraries. To extract these file, use any common zip utility. Or, you may use the Jar utility in the JDK's bin/ directory:
jar xvf src.zip

What's New in This Release:
Java SE 6u23 contains enhancements for your Java applications:
· Improved performance and stability
· Enhanced support for right-to-left languages
Java Hotspot VM 19.0:
· Java SE 6u23 includes version 19.0 of the Java HotSpot Virtual Machine with improvements to overall performance and reliability.
Java VisualVM 1.3.1:
Java VisualVM based on VisualVM 1.3.1 is included in Java SE 6u23. This release introduces the following features and enhancements:
· Added Java version and vendor information to the application Overview view
· Built on NetBeans Platform and profiler 6.9.1
Menu Item Corrections for Right-to-Left Languages:
· Several bugs in the non-default alignment and text orientation for the menu items in Swing have been fixed, as this is particularly important for right-to-left languages such as Arabic.
· Another issue corrected is the position of the icon and the text. For the non-default positions the text used to overlap the icon in a menu item, this is no longer the case.
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