1  import java.awt.Rectangle;

  2  

  3  /**

  4     This example demonstrates the difference between copying

  5     numbers and object references.

  6  */

  7  public class CopyDemo

  8  {

  9     public static void main(String[] args)

 10     {

 11        // Declare two object variables and copy the first into the second

 12  

 13        Rectangle box = new Rectangle(5, 10, 20, 30);

 14        Rectangle box2 = box;

 15        

 16        // Both variables refer to the same object

 17  

 18        System.out.print("box: ");

 19        System.out.println(box);

 20        System.out.print("box2: ");

 21        System.out.println(box2);

 22  

 23        System.out.println("Mutating box2");

 24        box2.translate(15, 25);

 25  

 26        // Both variables refer to the mutated object

 27  

 28        System.out.print("box: ");

 29        System.out.println(box);

 30        System.out.print("box2: ");

 31        System.out.println(box2);

 32  

 33        // Declare two number variables and copy the first into the second

 34  

 35        int luckyNumber = 13; 

 36        int luckyNumber2 = luckyNumber; 

 37  

 38        System.out.print("luckyNumber: ");

 39        System.out.println(luckyNumber);

 40        System.out.print("luckyNumber2: ");

 41        System.out.println(luckyNumber2);

 42        

 43        System.out.println("Changing luckyNumber2");

 44        luckyNumber2 = 12;

 45  

 46        // Only the second number changes.

 47  

 48        System.out.print("luckyNumber: ");

 49        System.out.println(luckyNumber);

 50        System.out.print("luckyNumber2: ");

 51        System.out.println(luckyNumber2);

 52     }

 53  }

 54  

 55  

 56