Java -Xmx, Max memory on system

My Java application runs another Java application, by running the process "java -jar j.jar". J.jar is known to use a LOT of memory depending on the dataset it is given, and often gets an OutOfMemoryError heap. So I want to use -Xmx on it, so that I can allocate as much memory as possible (or close to). I was thinking of getting the total memory on the system, then specifying 80-90% of that in -Xmx.

Is there any solution to my problem? And, how does my solution sound?

Edit: I cant reduce the memory consumption as the memory being used is by Java's built-in pack200 compression, which I am using to pack some JAR files.


  • Depending on your OS, this might work for getting the free and available memory size: mxbean =; sunmxbean = ( mxbean;
    long freeMemory = sunmxbean.getFreePhysicalMemorySize();
    long availableMemory = sunmxbean.getTotalPhysicalMemorySize();

    From there, you can figure out 80-90% and launch your jar with the max memory size you want.

    I don't know that this works with all OS's (i.e. Windows), but it worked when I tested it with both OSX and Linux.