INHERITANCE AND POLYMORPHISM - Java Programming: From Problem Analysis to Program Design - page 673

Next, consider the following application program:

public class SuperSubClassObjects
{

public static void main(String[] args)
{

RectangleShape rectangle, rectRef; //Line 1

BoxShape box, boxRef; //Line 2

rectangle = new RectangleShape(12, 4); //Line 3

System.out.println("Line 4: Rectangle \n"
+ rectangle+ "\n"); //Line 4

box = new BoxShape(13, 7, 4); //Line 5

System.out.println("Line 6: Box\n"
+ box+ "\n");

//Line 6

rectRef = box; //Line 7

System.out.println("Line 8: Box via rectRef\n"
+ rectRef+ "\n"); //Line 8

boxRef = (BoxShape) rectRef; //Line 9

System.out.println("Line 10: Box via boxRef\n"
+ boxRef + "\n"); //Line 10

if (rectRef instanceof BoxShape) //Line 11

System.out.println("Line 12: rectRef is "
+ "an instance of BoxShape"); //Line 12

else //Line 13

System.out.println("Line 14: rectRef is not "
+ "an instance of BoxShape"); //Line 14

if (rectangle instanceof BoxShape) //Line 15

1
0

System.out.println("Line 16: rectangle is "
+ "an instance of BoxShape"); //Line 16

else //Line 17

System.out.println("Line 18: rectangle is not "
+ "an instance of BoxShape");

//Line 18

}

}

Sample Run:

Line 4: Rectangle
Length = 12.0, Width = 4.0, Perimeter = 32.0, Area = 48.0

Line 6: Box
Length = 13.0, Width = 7.0, Height = 4.0, Surface Area = 342.0, Volume = 364.0

Line 8: Box via rectRef
Length = 13.0, Width = 7.0, Height = 4.0, Surface Area = 342.0, Volume = 364.0