1 // 测试继承                                      快捷键    ctrl+/ 单行注释      alt+/ 代码提示(syout main)    ctrl+shift+o 导入其它包的类
 2 package com.lk.oo;      //                                 Ctrl+ shift+L 全部快捷键    ctrl +D 删除单行代码
 3 class Person {
 4     int id;
 5     String name;
 6     public void rest(){
 7         System.out.println("休息一会");
 8     }
 9 }
10
11 class Student extends Person{
12     String major;
13     public  Student(int id,String name,String major){
14         this.id=id;
15         this.name=name;
16         this.major=major;
17     }
18     public void study(){
19         System.out.println("我在学习高数");
20     }
21 }
22
23 public class TestExtends {
24     public static void main(String args[]){
25         Student stu1=new Student(101,"李白","汉语言文学");
26         stu1.rest(); //调用父类Person的rest() 方法
27         System.out.println("id="+stu1.id+",名字："+stu1.name+",专业："+stu1.major);
28         //instanceof是二元运算符，左边是对象，右边是类；当对象是右边类或子类所创建对象时，返回true；否则，返回false
29         System.out.println(stu1 instanceof Student);
30         System.out.println(stu1 instanceof Person);
31         System.out.println(stu1 instanceof Object);  //显然stu1 属于Student类-->Person类-->Object类(继承关系)以上三个均会返回true
32
33         System.out.println(new Person() instanceof Student); //新建一个Person类的对象，显然他不是Student 这个类的对象
36
37     }
38
39 }

 1 package com.lk.oo;
 2 //方法的重写
 3 class Vehicle{
 4     public void run(){
 5         System.out.print("跑起来");
 6     }
 7
 8 }
 9 class Horse extends Vehicle{
10     public void run() { //重写父类的方法
11         System.out.println("哒哒哒。。。。");
12
13     }
14
15 }
16 public class TestOverride {
17     public static void main(String arg[]) {
18         Horse horse1=new Horse();
19         horse1.run();
20     }
21
22
23
24 }