【java基础--instanceof】

た入场券 2024-03-16 10:04 5阅读 0赞

instanceof 是 Java 的保留关键字。
    它的作用是测试它左边的对象是否是它右边的类的实例，返回 boolean 的数据类型。
    x instanceof y	  判断x是不是y的父类	返回 true or false
    编译是否通过看	x是否与y有父子关系

public class text {
        
        public static void main(String[] args) {
        
    
            //Object > String
            //Object > Person > Teacher
            //Object > Person > Student
    
    //        System.out.println(x instanceof y); x是不是y的父类判断true or false
    //        编译是否通过看x是否与y有父子关系
            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
    
    
            Object object1 = new Person();
            System.out.println(object1 instanceof Student);//false
            System.out.println(object1 instanceof Person);//true
            System.out.println(object1 instanceof Object);//true
            System.out.println(object1 instanceof Teacher);//false
            System.out.println(object1 instanceof String);//false
    
            Person person = new Student();
            System.out.println(person instanceof Student);//true
            System.out.println(person instanceof Person);//true
            System.out.println(person instanceof Object);//true
            System.out.println(person instanceof Teacher);//false
            //System.out.println(person instanceof String);//编译错误
    
            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);//编译错误
            //System.out.println(student instanceof String);//编译错误
        }
    }