how to get the min and max heap size settings of a JVM from within a Java program

max heap size:

Runtime.getRuntime().maxMemory();

Some other calculations which you may find interesting:

Runtime runtime = Runtime.getRuntime();
long maxMemory = runtime.maxMemory();
long allocatedMemory = runtime.totalMemory();
long freeMemory = runtime.freeMemory();
long totalFreeMemory = freeMemory + (maxMemory - allocatedMemory);
long usedMemory = maxMemory - totalFreeMemory;

You just need to use the Runtime object with Runtime.getRuntime() and then use methods like totalMemory() and freeMemory().