Demonstrate totalMemory(), freeMemory() and gc()

Here is a Java Program to Demonstrate totalMemory(), freeMemory() and gc().

class MemoryDemo {
  public static void main(String args[]) {
    Runtime r = Runtime.getRuntime();
    long mem1, mem2;
    Integer someints[] = new Integer[1000];

    System.out.println("Total memory is: " +
                       r.totalMemory());

    mem1 = r.freeMemory();
    System.out.println("Initial free memory: " + mem1);
    r.gc();
    mem1 = r.freeMemory();
    System.out.println("Free memory after garbage collection: "
                       + mem1);

    for(int i=0; i<1000; i++)
      someints[i] = new Integer(i); // allocate integers

    mem2 = r.freeMemory();
    System.out.println("Free memory after allocation: "
                       + mem2);
    System.out.println("Memory used by allocation: "
                       + (mem1-mem2));

    // discard Integers
    for(int i=0; i<1000; i++) someints[i] = null;

    r.gc(); // request garbage collection

    mem2 = r.freeMemory();
    System.out.println("Free memory after collecting" +
                       " discarded Integers: " + mem2);

  }
}

Output of Above Java Program
Total memory is: 16121856
Initial free memory: 15837912
Free memory after garbage collection: 16123344
Free memory after allocation: 16031528
Memory used by allocation: 91816
Free memory after collecting discarded Integers: 16123344