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?

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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.