定义一个抽象基类Shape3页.doc

/定义一个抽象基类Shape，其中包含area方法abstract class Shape public abstract double area();/定义Cirele并且继承Shape类，实现area方法class Circle extends Shapeprivate double r;public Circle(double r)this.r = r;public double area()return Math.PI*r*r;/定义Rectangle并且继承Shape类，实现area方法，并且对其进行重载class Rectangle extends Shapeprivate double r;private double length;public Rectangle(double r, double length)this.r = r;this.length = length;