Question

While using Java Options, i found they are of two types. One that has “-” as a prefix and another as “+”. For example:

-XX:-UseParallelGC

XX:+UseThreadPriorities

Is there some reason why we have both “+” as well as “-“. Initially, i thought that + would mean enabling while – would mean disabling. But, if we want any option disabled than why even pass it along the command line?

Answer 1

Initially, i thought that + would mean enabling while – would mean disabling.

This is correct, according to the official documentation: “Boolean options are turned on with -XX:+<option> and turned off with -XX:-<option>.”

But, if we want any option disabled than why even pass it along the command line?

That’s because some may be enabled and others disabled per default, and this may change between Java releases.