Fun with Polymorphism

.gitignore

*.class
*~
\#*\#
semantic.cache

Circle.java

public class Circle extends Shape {

    int radius;

    public Circle(int radius) {
	this.radius = radius;
    } // Circle

    @Override
    public double area() {
	return Math.PI * this.radius * this.radius;
    } // area


} // Circle

Driver.java

/**
 * Driver for the Polymorphism Examples
 *
 * @author Michael E. Cotterell <mepcotterell@gmail.com>
 */
public class Driver {

    public static void main(String[] args) {

	Shape c = new Circle(10);
	Shape r = new Rectangle(10, 30);
	Shape s = new Square(20);

	Shape[] array = new Shape[] { c, r, s };

	for (Shape shape: array) {
	    System.out.println("area is " + shape.area());
	}
        
    } // main
    
} // Driver

Rectangle.java

public class Rectangle extends Shape {

    int length, width;

    public Rectangle(int length, int width) {
	this.length = length;
	this.width = width;
    } // Rectangle

    @Override
    public double area() {
	return length * width;
    } // area

} // Rectangle

Shape.java

public abstract class Shape {

    public abstract double area();

} // Shape

Square.java

public class Square extends Rectangle {

    public Square(int length) {
	super(length, length);
    } // Square

} // Square