Difference between -XX:+UseParallelGC and -XX:+UseParNewGC

Question

They are algorithms for the young generation garbage collection.

The second one (UseParNewGC) gets activated automatically with the concurrent tenured generation ga

Answer 1

UseParNewGC usually knowns as "parallel young generation collector" is same in all ways as the parallel garbage collector (-XX:+UseParallelGC), except that its more sophiscated and effiecient. Also it can be used with a "concurrent low pause collector".

See Java GC FAQ, question 22 for more information.

Note that there are some known bugs with UseParNewGC