The following example program prints out both the total and free memory sizes, allocates a chunk of memory, and then prints the memory sizes again. If the initial size of your JVM’s heap is about 1 MB, you should see the total memory increase as the heap grows. The amount of free memory should change as a function of the amount of memory allocated and the increase in size of the heap.

 public final class HeapSize {  public static final int DATA_SIZE = 1024*1024;  public static final void printMemory(Runtime runtime) {    System.out.println("
Total Memory: " + runtime.totalMemory());    System.out.println("Free Memory : " + runtime.freeMemory());  }  public static final void main(String[] args) {    Runtime runtime;    byte[] data;    runtime = Runtime.getRuntime();    printMemory(runtime);    data = new byte[DATA_SIZE];    printMemory(runtime);  }}