Java-- 类型信息

 1 package typeinfo;
 2 
 3 import java.util.*;
 4 
 5 abstract class Shape{
 6     void draw(){ System.out.println(this + ".draw()");}
 7     abstract public String toString();
 8 }
 9 
10 class Circle extends Shape{
11     public String toString(){
12         return "Circle";
13     }
14 }
15 
16 class Square extends Shape{
17     public String toString(){
18         return "Square";
19     }
20 }
21 
22 class Triangle extends Shape{
23     public String toString(){
24         return "Triangle";
25     }
26 }
27 
28 
29 public class Shapes {
30     public static void main(String [] args){
31         List<Shape>  shapelist = Arrays.asList(
32                 new Circle(), new Square(),new Triangle());
33         for(Shape shape:shapelist)
34             shape.draw();
35     }
36 }

1 Circle.draw()
2 Square.draw()
3 Triangle.draw()