java基础知识不会啊，大家来瞅瞅啊

[young_ao]

public class MyTypeOf {

	public static void main(String[] args) {
		Map<String, Object> map = new HashMap<>();
		map.put("aa", 123);
		aa(map);
	}
	
	public static void aa(Map<String,Object> map) {
		System.err.println(map.get("aa") instanceof Integer);
		System.err.println(map.get("aa") instanceof Object);
	}

}

请问这体现了java的什么特性呢？为什么？

[皮卡皮卡屁卡丘]

    public class Test  
    {  
        public static void testInstanceof(Object x)  
        {  
            System.out.println("x instanceof Parent:  "+(x instanceof Parent));  
            System.out.println("x instanceof Child:  "+(x instanceof Child));  
            System.out.println("x getClass Parent:  "+(x.getClass() == Parent.class));  
            System.out.println("x getClass Child:  "+(x.getClass() == Child.class));  
        }  
        public static void main(String[] args) {  
            testInstanceof(new Parent());  
            System.out.println("---------------------------");  
            testInstanceof(new Child());  
        }  
    }  
    class Parent {  
      
    }  
    class Child extends Parent {  
      
    }  
    /* 
    输出: 
    x instanceof Parent:  true 
    x instanceof Child:  false 
    x getClass Parent:  true 
    x getClass Child:  false 
    --------------------------- 
    x instanceof Parent:  true 
    x instanceof Child:  true 
    x getClass Parent:  false 
    x getClass Child:  true 
    */  

[皮卡皮卡屁卡丘]

引用 1 楼 aaa_pikaqiu 的回复:

    public class Test  
    {  
        public static void testInstanceof(Object x)  
        {  
            System.out.println("x instanceof Parent:  "+(x instanceof Parent));  
            System.out.println("x instanceof Child:  "+(x instanceof Child));  
            System.out.println("x getClass Parent:  "+(x.getClass() == Parent.class));  
            System.out.println("x getClass Child:  "+(x.getClass() == Child.class));  
        }  
        public static void main(String[] args) {  
            testInstanceof(new Parent());  
            System.out.println("---------------------------");  
            testInstanceof(new Child());  
        }  
    }  
    class Parent {  
      
    }  
    class Child extends Parent {  
      
    }  
    /* 
    输出: 
    x instanceof Parent:  true 
    x instanceof Child:  false 
    x getClass Parent:  true 
    x getClass Child:  false 
    --------------------------- 
    x instanceof Parent:  true 
    x instanceof Child:  true 
    x getClass Parent:  false 
    x getClass Child:  true 
    */  

从程序输出可以看出,instanceof进行类型检查规则是:你属于该类吗？或者你属于该类的派生类吗？而通过getClass获得类型信息采用==来进行检查是否相等的操作是严格的判断。不会存在继承方面的考虑；

[Daisyiko]

多态

[沁海棠]

多态 楼上+1

[大牛大胃牛]

应该是多态性吧

[qq_39124490]

多态啊 我的哥

[晨曦遇晓]

多态 instanceof 表示该对象是否是其后面对象的实例对象或者子类