JDK 1.6 Notable New Features

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.

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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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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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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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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Increased Developer Productivity

• JDBC 4.0 support (JSR 221)
• Significant library improvements
• Improvements to the Java Platform Debug Architecture (JPDA) & JVM Tool Interface

Improved User Experience

• look-and-feel updates to better match underlying operating system
• Improved desktop performance and integration
• Enhanced internationalization support

PS: JDK 5 New Features
      http://dev2dev.bea.com/pub/a/2005/09/java_5_features.html