java instanceof ?????????

Posted 2021-02-14

?????????span   ??????   ??????   ??????   ??????   ??????   ??????   ?????????   pre   

???????????????java ??????instanceof ??????????????????????????????????????????????????????????????????????????????instanceof??????????????????????????????????????????????????????????????????????????????????????????????????????????????????

????????? 
result = object instanceof class 
????????? 
Result?????????????????? 
Object??????????????????????????????????????? 
Class????????????????????????????????????????????? 
????????? 
?????? object ??? class ????????????????????? instanceof ??????????????? true????????? object ??????????????????????????????????????? object ??? null???????????? false???

??????instanceof???Java????????????????????????????????????????????????

?????????????????????class?????????object????????????????????????????????????????????????????????????Java????????????????????????

?????????????????????class?????????object?????????????????????????????????????????????????????????????????????result????????????true??????????????????false?????????class????????????????????????????????????????????????false???

???????????????????????????

 interface Person {
    public void eat();
}

//?????????People

 class People implements Person {
    private int a=0;
    @Override
    public void eat() {
        System.out.println("======"+a);

    }

}

//??????xiaoming???

 class xiaoming extends People {
    private String name;

    @Override
    public void eat() {
        System.out.println("+++++++++");
    }
}

//?????????
class  Test {
    public static void main(String[] args) {
        People p = new People();
        xiaoming x = new xiaoming();
        System.out.println(p instanceof Person);
        System.out.println(p instanceof xiaoming);
        System.out.println(x instanceof Person);
        System.out.println(x instanceof People);


    }
}

 

???????????????

true
false
true
true