How to view the current heap size that an application is using?

Question

I think I increased my heap size to 1 GB in NetBeans since I changed the config to look like this:

netbeans_default_options=\"-J-Xmx1g ......

Answer 1

public class CheckHeapSize {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        long heapSize = Runtime.getRuntime().totalMemory(); 

        // Get maximum size of heap in bytes. The heap cannot grow beyond this size.// Any attempt will result in an OutOfMemoryException.
        long heapMaxSize = Runtime.getRuntime().maxMemory();

         // Get amount of free memory within the heap in bytes. This size will increase // after garbage collection and decrease as new objects are created.
        long heapFreeSize = Runtime.getRuntime().freeMemory(); 

        System.out.println("heapsize"+formatSize(heapSize));
        System.out.println("heapmaxsize"+formatSize(heapMaxSize));
        System.out.println("heapFreesize"+formatSize(heapFreeSize));

    }
    public static String formatSize(long v) {
        if (v < 1024) return v + " B";
        int z = (63 - Long.numberOfLeadingZeros(v)) / 10;
        return String.format("%.1f %sB", (double)v / (1L << (z*10)), " KMGTPE".charAt(z));
    }
}