Can UseCMSCompactAtFullCollection be used in Sun JDK6?

I have googl开发者_如何学编程ed a lot and it seems UseCMSCompactAtFullCollection can only be used in Sun JDK1.4.1. Is it right?

Or this is the default after JDk1.4.2?

from the 1.4.2 faq, my bold

Why is fragmentation a potential problem for the concurrent low pause collector? Normally the concurrent low pause collector does not copy nor compact the live objects. A garbage collection is done without moving the live objects. If fragmentation becomes a problem, allocate a larger heap. In 1.4.2 if fragmentation in the tenured generation becomes a problem, a compaction of the tenured generation will be done although not concurrently. In 1.4.1 that compaction will occur if the UseCMSCompactAtFullCollection option is turned on.

I suggest reading this entry from Jon Masamitsu's blog for an explanation of what is going on.