java基础之instanceof的用法详解

转载:http://09572.iteye.com/blog/1562277

博客分类： 
• JavaSe

instanceof  Java代码  

1. interface A{  
2.       
3. }  
4. class B implements A{  
5.        
6. }  
7. class C extends B{  
8.        
9. }  
10. public class Iinstanceof {  
11.   
12.     public static void main(String[] args) {  
13.         A ab=new B();  
14.         A ac=new C();  
15.         B bc=new C();  
16.         B bb=new B();  
17.         C cc=new C();  
18.         //对象实现一个接口，用这个对象和这个接口进行instanceof判断，都为true。  
19.         System.out.println("ab instanceof A="+(ab instanceof A));  
20.         System.out.println("ac instanceof A="+(ac instanceof A));  
21.         System.out.println("bc instanceof A="+(bc instanceof A));  
22.         System.out.println("bb instanceof A="+(bb instanceof A));  
23.         System.out.println("cc instanceof A="+(cc instanceof A));  
24.         //对象和父类进行instanceof判断，都为true  
25.         System.out.println("ab instanceof B="+(ab instanceof B));  
26.         System.out.println("ac instanceof B="+(ac instanceof B));  
27.         System.out.println("bc instanceof B="+(bc instanceof B));  
28.         System.out.println("bb instanceof B="+(bb instanceof B));  
29.         System.out.println("cc instanceof B="+(cc instanceof B));  
30.         //对象和他的子类进行instanceof判断为false  
31.         System.out.println("ab instanceof C="+(ab instanceof C));  
32.         System.out.println("ac instanceof C="+(ac instanceof C));  
33.         System.out.println("bc instanceof C="+(bc instanceof C));  
34.         System.out.println("bb instanceof C="+(bb instanceof C));  
35.         System.out.println("cc instanceof C="+(cc instanceof C));  
36.     }  
37. }  

程序输出：
ab instanceof A=true
ac instanceof A=true
bc instanceof A=true
bb instanceof A=true
cc instanceof A=true
ab instanceof B=true
ac instanceof B=true
bc instanceof B=true
bb instanceof B=true
cc instanceof B=true
ab instanceof C=false
ac instanceof C=true
bc instanceof C=true
bb instanceof C=false
cc instanceof C=true