主程序App.java
public class App { public static void main(String[] args) { //Object > String //Object > Person > Teacher //Object > Person > Student Object object = new Student(); System.out.println(object instanceof Object); //true System.out.println(object instanceof Person); //true System.out.println(object instanceof Student); //true System.out.println(object instanceof Teacher); //false System.out.println(object instanceof String); //false System.out.println("-----------------------------"); Person person = new Student(); System.out.println(person instanceof Object); //true System.out.println(person instanceof Person); //true System.out.println(person instanceof Student); //true System.out.println(person instanceof Teacher); //false //System.out.println(person instanceof String); //编译报错 System.out.println("-----------------------------"); Student student = new Student(); System.out.println(student instanceof Object); //true System.out.println(student instanceof Person); //true System.out.println(student instanceof Student); //true //System.out.println(student instanceof Teacher); //编译报错 //System.out.println(person instanceof String); //编译报错 } }
Object类是所有类的父类
Person.java
类默认继承Object
类
public class Person { }
子类Teacher.java
继承Person
类
public class Teacher extends Person{ }
子类Student.java
继承Person
类
public class Student extends Person{ }
执行结果
true true true false false ------- true true true false ------- true true true