Java SE 6 is the current major release of the Java SE platform. Sun endeavors to foster the highest level of transparency and collaboration on the platform with the Java community through Project JDK 6, resulting in the following key features.
Download Java SE 6：
http://java.sun.com/javase/downloads/index.jsp
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1)New Security Features and Enhancements
Native platform Security (GSS/Kerberos) integration.
Java Authentication and Authorization Service (JAAS) login module that employs LDAP authentication
New Smart Card I/O API
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2)Integrated Web Services
New API for XML digital signature services for secure web services
New Client and Core Java Architecture for XML-Web Services (JAX-WS) 2.0 APIs
New support for Java Architecture for XML Binding (JAXB) 2.0
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3)Scripting Language Support (JSR 223)
New framework and API for scripting languages
Mozilla Rhino engine for JavaScript built into the platform
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4)Enhanced Management and Serviceability
Improved JMX Monitoring API
Runtime Support for dTrace (Solaris 10 and future Solaris OS releases only)
Improved memory usage analysis and leak detection
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5)Increased Developer Productivity
JDBC 4.0 support (JSR 221)
Significant library improvements
Improvements to the Java Platform Debug Architecture (JPDA) & JVM Tool Interface
6)Improved User Experience
look-and-feel updates to better match underlying operating system
Improved desktop performance and integration
Enhanced internationalization support
An in-depth summary of Java SE 6 features and enhancements to the platform is provided in the Java SE Umbrella JSR (JSR 270) and the desktop and core feature overviews.
note: this article is from http://java.sun.com/javase/6/features.jsp