继续画图形

package polymorphism;

public  class Shapes{   

 void draw(){}

   void erase(){}

 }  

 

package polymorphism;

public class Square extends Shapes {

 public void draw(){System.out.println("Square.draw");}

 public void erase(){System.out.println("Square.erase");}

 }

 

package polymorphism;

public class riangle extends Shapes {  

 public void draw(){    System.out.println("riangle.draw");   }

  public void erase(){    System.out.println("riangle.erase");  }

 }

 

package polymorphism;

public class Circle extends Shapes {

  public void draw(){    System.out.println("Circle.draw");}  

public void erase(){System.out.println("Circle.erase");}

  }

package polymorphism;

import java.util.Random;

public class RandomShapeGenerator {  

 private Random rand=new Random(47);

  public Shapes next(){   

 switch(rand.nextInt(3)){  

  default:    case 0:return new Circle();   

case 1:return new riangle();

   case 2:return new Square();    

 }     } }

package polymorphism;

public class Shape {

  private static RandomShapeGenerator gen=new RandomShapeGenerator();  

 public static void main(String args[]){  

 Shapes []s=new Shapes[9];   for(int i=0;i<s.length;i++)

   s[i]=gen.next();

   for(Shapes shp:s);  

  shp.draw();    

} }