// Fig. 9.6: InheritanceTest.java
// Demonstrating the "is a" relationship

// Java core packages
import java.text.DecimalFormat;

// Java extension packages
import javax.swing.JOptionPane;

public class InheritanceTest {

   // test classes Point and Circle
   public static void main( String args[] )
   {
      Point point1, point2; 
      Circle circle1, circle2;

      point1 = new Point( 30, 50 );
      circle1 = new Circle( 2.7, 120, 89 );

      String output = "Point point1: " + point1.toString() +
         "\nCircle circle1: " + circle1.toString();
   
      // use "is a" relationship to refer to a Circle
      // with a Point reference
      point2 = circle1;   // assigns Circle to a Point reference

      output += "\n\nCircle circle1 (via point2 reference): " +
         point2.toString();

      // use downcasting (casting a superclass reference to a
      // subclass data type) to assign point2 to circle2
      circle2 = ( Circle ) point2;

      output += "\n\nCircle circle1 (via circle2): " +
         circle2.toString();

      DecimalFormat precision2 = new DecimalFormat( "0.00" );
      output += "\nArea of c (via circle2): " +
         precision2.format( circle2.area() );

      // attempt to refer to Point object with Circle reference
      if ( point1 instanceof Circle ) {
         circle2 = ( Circle ) point1;  
         output += "\n\ncast successful";
      }
      else
         output += "\n\npoint1 does not refer to a Circle";

      JOptionPane.showMessageDialog( null, output,
         "Demonstrating the \"is a\" relationship",
         JOptionPane.INFORMATION_MESSAGE );

      System.exit( 0 );
   }

}  // end class InheritanceTest 


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 * (C) Copyright 2002 by Deitel & Associates, Inc. and Prentice Hall.     *
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