Memory usage in Java can be misleading. Some versions of the JVM will happily take ALL your free RAM if it thinks it's sitting there unused because there's a RA

Memory usage in Java can be misleading. Some versions of the JVM will happily take ALL your free RAM if it thinks it's sitting there unused because there's a RAM/CPU tradeoff in garbage collected systems: the less frequently you GC the less CPU time you burn and the faster the app runs. If your machine actually does have gobs of free RAM, it therefore makes sense for Java to use all of it. If your machine has gobs of free RAM you were planning on using for something else after your Java app started, well, that's something the JVM couldn't know. Some versions (on Windows?) monitor free memory and adjust down its own usage if you seem to be consuming the headroom, but on other platforms, you just have to tell Java it's got a limit and can't go beyond it.