12.instanceof和类型转换

1 package com.oop.demo07;
2 
3 public class Person {
4 
5     public void run(){
6         System.out.println("run");
7     }
8 
9 }

1 package com.oop.demo07;
2 
3 public class Student extends Person {
4 
5     public void go() {
6         System.out.println("go");
7     }
8 
9 }

1 package com.oop.demo07;
2 
3 public class Teacher extends Person{
4 }

 1 package com.oop;
 2 
 3 import com.oop.demo07.Person;
 4 import com.oop.demo07.Student;
 5 import com.oop.demo07.Teacher;
 6 public class Application {
 7 
 8     public static void main(String[] args) {
 9 
10         //Object > String
11         //Object > Person > Teacher
12         //Object > Person > Student
13         Object object = new Student();
14 
15         //System.out.println(X instanceof Y);//能不能编译通过！取决于X和Y之间是否存在父子关系！
16         System.out.println(object instanceof Student);//true
17         System.out.println(object instanceof Person);//true
18         System.out.println(object instanceof Object);//true
19         System.out.println(object instanceof Teacher);//False
20         System.out.println(object instanceof String);//False
21         System.out.println("================================");
22         Person person = new Student();
23         System.out.println(person instanceof Student);//true
24         System.out.println(person instanceof Person);//true
25         System.out.println(person instanceof Object);//true
26         System.out.println(person instanceof Teacher);//False
27         //System.out.println(person instanceof String);//编译报错
28         System.out.println("================================");
29         Student student = new Student();
30         System.out.println(student instanceof Student);//true
31         System.out.println(student instanceof Person);//true
32         System.out.println(student instanceof Object);//true
33         //System.out.println(student instanceof Teacher);//编译报错
34         //System.out.println(student instanceof String);//编译报错
35 
36     }
37 }