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

Question

What is the difference between -XX:+UseParallelGC and -XX:-UseParallelGC? Most links indicate the first, but http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html mentions the second.

Thank you.

Answer 1

From the documentation:

Boolean options are turned on with -XX:+<option> and turned off with -XX:-<option>

So it means that -XX:+UseParallelGC will turn on the parallel garbage collection, and -XX:-UseParallelGC will turn it off.

Answer 2

The line:

-XX:+UseParallelGC

Enables the ParallelGC. Note the + sign

The line:

-XX:-UseParallelGC

Disables it. Note the - sign.