java多态代码

 1 class Shape {
 2     public double perimeter = 0.0;
 3     public double perimeter(){
 4     return perimeter;
 5     }
 6 }
 7 
 8 class Circle extends Shape{
 9     public double r = 0.0;
10     public Circle(double r){
11         this.r=r;        
12     }
13     public double perimeter(){
14         perimeter = 2*3.14*r*r;
15         return perimeter;
16     }
17 }
18 
19 class Square extends Shape{
20     public double l = 0.0;
21     public double w = 0.0;
22     public Square(double l,double w){
23         this.l=l;
24         this.w=w;
25     }
26     public double perimeter(){
27         perimeter = 2*(l+w);
28         return perimeter;
29     }
30 }
31 
32 class Perimeter{
33     public static void main(String[] args){
34         Shape s1 = new Circle(2.2);
35         System.out.println(s1.perimeter());
36         s1 = new Square(2,3);
37         System.out.println(s1.perimeter());
38         System.out.println(s1.perimeter);
39     }
40 }