Are Java 6's performance improvements in the JDK, JVM, or both?

Question

I\'ve been wondering about the performance improvements touted in Java SE 6 - is it in the compiler or the runtime? Put another way, would a Java 5 application compiled by J

Answer 1

There's been a lot of new improvements and optimization in the new java virtual machine. So the main part you'll see improved performance is while running java with the version 6 jvm.

Compiling old java code using the Java 6 JDK will probably yield more efficient code, but the main improvements lie in the virtual machine, at least that's what I've noticed.