Java Command Line Options

[chander shivdasani]

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?

[chander shivdasani]

I figured the answer:

"Initially, i thought that + would mean enabling while - would mean disabling"

The official documentation suggests that these options are turned on/off with +/-

"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.

[Campbell Ritchie]

Most command-line tools have a - before their options.

[Wouter Oet]

The + and - can be used to turn on and off boolean options of the jvm. For a list of options of the java jvm see this.