java.instanceof

package Demo.oop.APP.Demo05;

public class application {
    public static void main(String[] args) {
        //object>String
        //Object>Person>student
        //Object>Person>Teacher
        Object object = new Student();
        Person person=new Student();
        System.out.println(object instanceof Student );//true
        System.out.println(object instanceof Person);//true
        System.out.println(object instanceof Teacher);//false
        System.out.println(object instanceof String);//false
        System.out.println("=====================");
        System.out.println(person instanceof Student);//ture
        System.out.println(person instanceof Teacher);//false
        //System.out.println(person instanceof String);//编译报错
    }
}
/**
 * 1.父类引用指向子类对象
 * 2.把子类转为父类，向上转型
 * 3.把父类转换为子类，向下转换，强制转换
 * 4.方便方法调用，减少代码重复
 * 抽象-->封装，继承，多态
 */

　　

package Demo.oop.APP.Demo05;

public class Person {

}

　　

package Demo.oop.APP.Demo05;

public class Student extends Person{

}

　　

package Demo.oop.APP.Demo05;

public class Teacher extends Person{
}