instanceof和类型转换

什么是instanceof

判断一个对象是什么类型

注意点

X 和 Y 必须要有父子关系 否则编译都会失败
X对象只要是Y的子类(无论 是 儿子 还是 孙子 还是 曾孙。。。。)X instanceof Y = true

示例

package com.oop;

import com.oop.demo08.Student;

import com.oop.demo08.Person;

import com.oop.demo08.Teacher;

public class Applcation {

    public static void main(String[] args) {

        // instanceof练习

        /*

        * 多态 父类的引用 指向子类的实例

        * student是Object的子类(相当于孙子)

        * Person是Object的子类

        * Student是person的子类

        * */

        // Object > String

        // Object > Person > Student

        // Object > Person > Teacher

        Object object = new Student();

        System.out.println(object instanceof Student); // true

        System.out.println(object instanceof Person);  // true

        System.out.println(object instanceof Object);  // true

        System.out.println(object instanceof Teacher); // false

        System.out.println(object instanceof String);  // false

        System.out.println("=======================");

        Person p = new Student();

        System.out.println(p instanceof Student); // true

        System.out.println(p instanceof Person);  // true

        System.out.println(p instanceof Object);  // true

        System.out.println(p instanceof Teacher); // false

        //System.out.println(p instanceof String);  // 编译失败

        System.out.println("=======================");

        Student student = new Student();

        System.out.println(student instanceof Student); // true

        System.out.println(student instanceof Person);  // true

        System.out.println(student instanceof Object);  // true

        //System.out.println(student instanceof Teacher); // 编译失败

        //System.out.println(p instanceof String);  // 编译失败

    }

}

instanceof和类型转换的相关教程结束。