Equivalence of Aliases

two variables, both pointing at the same object

Here is the example program (again!) with this modification:

import java.awt.*;
class EqualsDemo4
{
  public static void main ( String arg[] )
  {
    Point pointA = new Point( 7, 99 );     // pointA refers to a Point Object
    Point pointB = pointA;                 // pointB refers to the same Object 

    if ( pointA.equals( pointB ) )
    {
      System.out.println( "The two variables refer to the same object," );
      System.out.println( "or different objects with equivalent data." );
    }
    else
      System.out.println( "The two variables refer to different objects" );     

  }
}

The picture of the situation is the same as before. But now the equals() method is used. It:

Uses the reference pointA to get the x and y from the object.
Uses the reference pointB to get the x and y from the same object.
Determines that the two x's are the same and that the two y's are the same.
Returns a true.

The fact that the object is the same object in step 1 and step 2 does not matter. The x's that are tested are the same, and the y's that are tested are the same, so the result is true.

QUESTION 21:

If the == operator returns a true will the equals() method return a true, always?

Answer:

Equivalence of Aliases

QUESTION 21: