There was a comment in the question [calling-system-gc-explicitly](https://stackoverflow.com/questions/4784987/calling-system-gc-explicitly/4785123#4785123) stating that "*You can not "force" a generic JVM to do garbage collection because a garbage collector is not actually required by the JVM spec.*". My question is if there's such a JVM (and how and where does it get used, if so).