java中的instanceof关键字总结

interface A{    

}    
class B implements A{    

}    
class C extends B{    

}    
public class Iinstanceof {    

    public static void main(String[] args) {    
        A ab=new B();    
        A ac=new C();    
        B bc=new C();    
        B bb=new B();    
        C cc=new C();    
        //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。    
        System.out.println("ab instanceof A="+(ab instanceof A));    
        System.out.println("ac instanceof A="+(ac instanceof A));    
        System.out.println("bc instanceof A="+(bc instanceof A));    
        System.out.println("bb instanceof A="+(bb instanceof A));    
        System.out.println("cc instanceof A="+(cc instanceof A));    
        //对象和父类进行instanceof判断，都为true    
        System.out.println("ab instanceof B="+(ab instanceof B));    
        System.out.println("ac instanceof B="+(ac instanceof B));    
        System.out.println("bc instanceof B="+(bc instanceof B));    
        System.out.println("bb instanceof B="+(bb instanceof B));    
        System.out.println("cc instanceof B="+(cc instanceof B));    
        //对象和他的子类进行instanceof判断为false    
        System.out.println("ab instanceof C="+(ab instanceof C)); //打印false 
        System.out.println("ac instanceof C="+(ac instanceof C));    
        System.out.println("bc instanceof C="+(bc instanceof C));    
        System.out.println("bb instanceof C="+(bb instanceof C));//打印false    
        System.out.println("cc instanceof C="+(cc instanceof C));    
    }    
}    

总结：

java的instanceof关键词，用于判断子类是否是父类的实例，实现的可以是接口，也可以是实现的父类。