instance------判断一个对象是什么类型，两个之间是否有父子关系

public class Person {
}

public class Student extends Person{
}

public class Teacher extends Person {
}


public class Amplication {

    public static void main(String[] args) {
        Object object = new Student();

        //instance  判断 = 号两边是否有父子关系
        System.out.println(object instanceof Student); // true   object是Student类的一个实例化
        System.out.println(object instanceof Person);  //true
        System.out.println(object instanceof Object);  // true
        System.out.println(object instanceof Teacher); //false
        System.out.println("================================");

        //new一个Student类的实例，但是属于Person类
        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("=================================");

        //new一个Student类的实例化，但属于Teacher类
        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); //false
    }
    }