Is there a way to find the class objects memory size?

Question

Hi Friends,
Please help.
Is there a way to find the number of Objects created and total size?
For example:
class AgeRecord
int start;
int end;
AgeRecord(int start, int end)
this.start = start;
this.end = end;
In a loop if I create 1000 objects, how will I get the total memory size
Thanks and Regards
JG

Answer 1

You might find this useful...
package forums;
http://weblogs.java.net/blog/dwalend/archive/2007/11/the_thing_about.html
http://forums.sun.com/thread.jspa?threadID=457279&start=30&tstart=0
http://www.velocityreviews.com/forums/t364574-size-of-boolean-type.html
The JLS doesn't specify the size of a boolean, leaving it upto the JVM
implementor to define. Sun's JVM stores booleans as:
(1) a boolean is-an int; i.e. a signed 32 bit twos-compliment integer.
    At face value, this is an innordinate waste of space, but Java uses a
    32-bit stack frame, and most (modern) CPU's use a 32-bit word anyway,
    so the wasted space is worth the CPU cycles, and it's simple.
(2) a boolean[] is-a byte array, using 1 byte per element, rounded up to the
    nearest 8, plus 8 bytes for the array-object itself.
    For example: boolean[] bools = boolean[100];
    100 mod 8 = 4; so that'd be 104 bytes + 8 bytes = 112 bytes.
    So, let's dis/prove the contention by experiment.
    1,000,000 mod 8 = 0 so 1,000,000 + 8 bytes for the array = 1,000,008
class BooleanArraySizeTest
  public static void main(String[] args) {
    final Runtime rt = Runtime.getRuntime();
    System.out.println("The contention is that each iteration should use 1,000,008 bytes.");
    try {
      long before, after;
      final int TIMES = 32;
      boolean[][] bools = new boolean[TIMES][];
      for (int i=0; i<TIMES; i++) {
        before = rt.totalMemory() - rt.freeMemory();
        int n = 1000*1000-(TIMES/2)+i;
        bools[i] = new boolean[n];
        after = rt.totalMemory() - rt.freeMemory();
        System.out.print(n);
        System.out.print('\t');
        System.out.print(after-before);
        System.out.println();
    } catch (Exception e) {
      e.printStackTrace();
999984 used=1000000 bytes
999985 used=1000000 bytes
999986 used=1000000 bytes
999987 used=1000000 bytes
999988 used=1000000 bytes
999989 used=1000008 bytes
999990 used=1000008 bytes
999991 used=1000008 bytes
999992 used=1000008 bytes
999993 used=1000008 bytes
999994 used=1000008 bytes
999995 used=1000008 bytes
999996 used=1000008 bytes
999997 used=1000016 bytes
999998 used=1000016 bytes
999999 used=1000016 bytes
1000000 used=1000016 bytes
1000001 used=1000016 bytes
1000002 used=1000016 bytes
1000003 used=1000016 bytes
1000004 used=1000016 bytes
1000005 used=1000024 bytes
1000006 used=1000024 bytes
1000007 used=1000024 bytes
1000008 used=1000024 bytes
1000009 used=1000024 bytes
1000010 used=1000024 bytes
1000011 used=1000024 bytes
1000012 used=1000024 bytes
1000013 used=1000032 bytes
1000014 used=1000032 bytes
1000015 used=1000032 bytes
ENVIRONMENT:
  Microsoft Windows [Version 6.0.6000]
  Copyright (c) 2006 Microsoft Corporation.  All rights reserved.
  C:\Users\Administrator>java -version
  java version "1.6.0_12"
  Java(TM) SE Runtime Environment (build 1.6.0_12-b04)
  Java HotSpot(TM) Client VM (build 11.2-b01, mixed mode, sharing)
*/Cheers. Keith.