10-instanceof

 1 package com.example;
 2 class A{
 3     void tell1(){
 4         System.out.println("this is tell1-A");
 5     }
 6 }
 7 class B extends A{
 8     void tell2(){
 9         System.out.println("this is tell2-B");
10     }
11 }
12 public class MyClass {
13     public static void main(String[] args){
14     //在JAVA中可以使用INSTANCEOF关键字判断一个对象到底是不是一个类的实例
15         B b = new B();
16         A a = b;
17         System.out.println(a instanceof A);
18         System.out.println(a instanceof B);
19 
20         System.out.println(b instanceof A);
21         System.out.println(b instanceof B);
22     }
23 }