多态例子

一）相关类

class  A  ... {
         public String show(D obj)...{
                return ("A and D");
         } 
         public String show(A obj)...{
                return ("A and A");
         } 
}  
class  B  extends  A ... {
         public String show(B obj)...{
                return ("B and B");
         }
         public String show(A obj)...{
                return ("B and A");
         } 
}
class  C  extends  B ... {}  
class  D  extends  B ... {}  

（二）问题：以下输出结果是什么？

         A a1  =   new  A();
        A a2  =   new  B();
        B b =  new  B();
        C c  =   new  C(); 
        D d  =   new  D(); 
         System.out.println(a1.show(b));   ①
        System.out.println(a1.show(c));   ②
        System.out.println(a1.show(d));   ③
        System.out.println(a2.show(b));   ④
        System.out.println(a2.show(c));   ⑤
        System.out.println(a2.show(d));   ⑥
        System.out.println(b.show(b));     ⑦
        System.out.println(b.show(c));     ⑧
        System.out.println(b.show(d));     ⑨    

（三）答案

              ①   A and A
              ②   A and A
              ③   A and D
              ④   B and A
              ⑤   B and A
              ⑥   A and D
              ⑦   B and B
              ⑧   B and B
              ⑨   A and D

 

转摘http://blog.youkuaiyun.com/thinkGhoster/article/details/2307001