接口的应用Shape类，Rectangle、Triangle、Square

import java.io.*; public class Test { public static void main(String[] args) { Circle circle=new Circle(); Trangle trangle= new Trangle(); Square square=new Square(); Shape shape1=new Shape(); Shape[]myshape={circle,trangle,square}; shape1.draw(); shape1.erase(); myshape[0].draw(); myshape[0].erase(); myshape[1].draw(); myshape[1].erase(); myshape[2].draw(); myshape[2].erase(); } } class Shape { /** * The constructor for class Shape */ public Shape() { System.out.println("Inside constructor of Shape"); } /** * The draw method can not draw anything because it has nothing to draw. */ public void draw() { System.out.println("The draw method in Shape"); } /** * The erase method can not erase anything because it has nothing to * erase. */ public void erase() { System.out.println("The erase method in Shape"); } } class Circle extends Shape { public Circle() { System.out.println("Inside constructor of Circle"); } public void draw() { System.out.println("The draw method in Circle"); } /** * The erase method can not erase anything because it has nothing to * erase. */ public void erase() { System.out.println("The erase method in Shape"); } } class Square extends Shape { public Square() { System.out.println("Inside constructor of Square"); } public void draw() { System.out.println("The draw method in Square"); } /** * The erase method can not erase anything because it has nothing to * erase. */ public void erase() { System.out.println("The erase method in Shape"); } } class Trangle extends Shape { public Trangle() { System.out.println("Inside constructor of Trangle"); } public void draw() { System.out.println("The draw method in Trangle"); } /** * The erase method can not erase anything because it has nothing to * erase. */ public void erase() { System.out.println("The erase method in Shape"); } }