Force JVM to garbage collect externally?

I'm running PS3 Media Server on Arch Linux, and it's using quite a bit of memory that I'm sure could be collected if the JVM would just try. Is there any way for me to get the process to garbage collect? Maybe I there's a signal I can send to it?

>>13
The application is a client, it works with large streams of data, after which those streams are released, in the sense that you won't make use of them. The application is supposed to be in a "clean" slate after all of these streams have been released, yet I see some extra 1GB memory usage after a days usage - 1GB of memory which will never be used by the application again, and can't be used in any way by the user - restarting the application would return it back to the same exact state, except now it only uses 40MB. It's clearly a leak of sorts, but a restart is only a hotkey away, so it's not really a major concern for me right now.