/** Demo difference between primitive and object type.

    Arguments are passed by value.  A variable assigned an object actually
    contains a _reference_ (think memory address) of the object.
*/
public class PrimitiveVsObject
{
   /** Set value of a die, the caller can observe the change.  */
   private static void setDieValue(Die d)
   {
      System.out.println(d + " d.value = " + d.getValue());
      d.setValue(2);
      System.out.println(d + " d.value = " + d.getValue());
   }

   /** Reassign a new die, the caller doesn't know what happened. */
   private static Die reassignDie(Die d)
   {
      System.out.println(d + " d.value = " + d.getValue());
      d = new Die(120); // 120-sided die
      System.out.println(d + " d.value = " + d.getValue());
      d.setValue(3); // changing local d, reassigned.
      System.out.println(d + " d.value = " + d.getValue());
      return d;
   }

   /** No way for a caller to see a change of a primitive. */
   private static void changeInt(int i)
   {
      System.out.println("i = " + i);
      i++;
      System.out.println("i = " + i);
   }

   public static void main(String[] args)
   {
      Die die1 = new Die(6); // 6-sided die
      die1.setValue(1);
      System.out.println("before: " + die1 + " die1.value = " + die1.getValue());
      System.out.println();

      setDieValue(die1);
      System.out.println("after: " + die1 + " die1.value = " + die1.getValue());
      System.out.println();

      Die die2 = reassignDie(die1);
      System.out.println("again: " + die1 + " die1.value = " + die1.getValue());
      System.out.println("again: " + die2 + " die2.value = " + die2.getValue());
      System.out.println();

      int primitiveNumber = 23;
      System.out.println("primitiveNumber = " + primitiveNumber);
      changeInt(primitiveNumber);
      System.out.println("primitiveNumber = " + primitiveNumber);
   }
}