J2se 6 Update 14 Now

: A new optimization ( -XX:+DoEscapeAnalysis ) allowed the compiler to determine if an object is "escaped" (used outside a method). If it isn't, the JVM can allocate the object on the stack instead of the heap, significantly speeding up execution and reducing garbage collection overhead.

: The -XX:+UseCompressedOops option was introduced to improve the performance of 64-bit JREs on heaps smaller than 32GB. It allows 64-bit JVMs to use 32-bit references, reducing memory footprint and improving cache efficiency. J2Se 6 Update 14

: The update included enhancements to the parallel compacting collector to increase overall application throughput. Stability and Platform Support : A new optimization ( -XX:+DoEscapeAnalysis ) allowed

This update featured , which integrated several optimizations originally slated for later versions like Java 7. It allows 64-bit JVMs to use 32-bit references,

Java SE 6 Update 14 Release Notes. - Oracle