Version History of Java 6 Update 21

Additional Supported System Configurations

For Java SE 6u21, support has been added for the following system configurations:

  • Oracle Enterprise Linux 5.5
  • Oracle Enterprise Linux 5.4
  • Oracle Enterprise Linux 4.8
  • Red Hat Enterprise Linux 5.5
  • Red Hat Enterprise Linux 5.4
  • Oracle VM 2.2.0.0.0
  • Google Chrome 4.0

Support for Customized Loading Progress Indicators

With Java SE 6u21, you can now enhance the loading experience of an application by providing a customized loading progress indicator (sometimes referred to as a progress bar) to better inform the end user of how much of the application has been downloaded during startup.
Java Hotspot VM 17.0

Java SE 6u21 includes version 17.0 of the Java HotSpot Virtual Machine with improvements to overall quality and features such as compressed object pointers, escape analysis-based optimization, code cache management, the Concurrent Mark-Sweep garbage collector and its successor, the Garbage First (G1) garbage collector. (G1 continues to be available in Early Access via the -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC flag. See the G1 technology page for more information.)
Java VisualVM

Java VisualVM based on VisualVM 1.2.2 is included in Java SE 6u21. This release introduces the following features and enhancements:

  • HeapWalker performance improvements
  • VisualVM-Sampler performance improvements
  • BTrace4VisualVM plugin introduces BTrace 1.1
  • Profiling engine bugfixes
  • Built on NetBeans Platform 6.8

Security Exception Upon Drag-and-Drop

Drag-and-drop would, under certain circumstances, result in a null value being passed instead of the expected data.
Java SE 6u21 provides a fix that lets drag-and-drop operations succeed for signed applications or applications with the accessClipboard permission granted.
Bug Fixes

Java SE 6 Update 21 does not contain any additional fixes for security vulnerabilities to its previous release, Java SE 6 Update 20. Users who have Java SE 6 Update 20 have the latest security fixes and do not need to upgrade to this release to be current on security fixes.