Object size calculation in Java

ObjectSizeCalcTest.java

import java.util.ArrayList;
import java.util.List;

public class ObjectSizeCalcTest {

   static class Employee {
      public int age;
      public int id;
      public String name;
      public Employee(int age, int id, String name) {
         super();
         this.age = age;
         this.id = id;
         this.name = name;
      }      
   }
   
   private static void print(String msg, Object o){
      System.out.println(msg+" -> "+ObjectSizeCalculator.getObjectSize(o));
   }
   
   public static void main(final String[] args) {
      Employee e1 = new Employee(30,87987,"Ramasubramanian");
      Employee e2 = new Employee(54,879800,"Sankar");
      Employee e3 = new Employee(23, 364767, "Adithya");
      print("E1 size",e1);
      print("E2 size",e2);
      print("E3 size",e3);
      List<Employee> l = new ArrayList<ObjectSizeCalcTest.Employee>();
      l.add(e1);
      l.add(e2);
      print("Default list size with e1 and e2",l);
      l.add(e1);
      print("Default list size with 2 e1 and 1 e2",l);
      l.add(e3);
      print("Default list size with 2 e1,1 e2 and 1 e3",l);
      List<Employee> l2 = new ArrayList<ObjectSizeCalcTest.Employee>(2);
      l2.add(e1);
      l2.add(e2);
      l2.add(e3);
      print("Predefined sized list size with 1 e1,1 e2 and 1 e3",l2);
   }
   
}

Output :
E1 size -> 96
E2 size -> 72
E3 size -> 80
Default list size with e1 and e2 -> 248
Default list size with 2 e1 and 1 e2 -> 248
Default list size with 2 e1,1 e2 and 1 e3 -> 328
Predefined sized list size with 1 e1,1 e2 and 1 e3 -> 304

Link to ObjectSizeCalculator.java from twitter -> https://github.com/twitter/commons/blob/master/src/java/com/twitter/common/objectsize/ObjectSizeCalculator.java