1 import java.util.Map;
 2 import java.util.HashMap;
 3 import java.util.Observer;
 4 import java.util.Observable;
 5 
 6 //学生类(Student)继承Observable后变得可以被观察
 7 class Student extends Observable{
 8     //属性
 9     private String name;
10     private boolean isSleep = false;
11     private boolean isLate = false;
12     //构造函数
13     public Student(){}
14     public Student(String name){
15         this.name = name;
16     }
17     //睡觉行为
18     public void sleep(){
19         System.out.println(name + " is sleeping");
20         isSleep = true;
21         setChanged();
22         notifyObservers("sleep");
23         
24     }
25     //迟到行为
26     public void late(){
27         System.out.println(name + " was lated");
28         isLate = true;
29         setChanged();
30         notifyObservers("late");
31     }
32 }
33 //教师类(Teacher)实现Observer接口成为观察者
34 class Teacher implements Observer{
35     //参数arg作为key，该参数触发的回应作为value存储在Map中
36     private Map<String,String> info = new HashMap<String,String>();
37     public Teacher(){
38         info.put("sleep","wakeup!wakeup!");
39         info.put("late","come in.");
40     }
41     //添加键值对
42     public boolean addSay(String k,String v){
43         return info.put(k,v)==null?false:true;
44     }
45     @Override
46     public void update(Observable o,Object arg){
47             String say = info.get(arg);
48             if(say == null){
49                 return;
50             }
51             System.out.println("teacher: "+say);
52     }
53 }
54 //班主任类(ClassHead)实现Observer接口成为观察者
55 class ClassHead implements Observer{
56     private Map<String,String> info = new HashMap<String,String>();
57     public ClassHead(){
58         info.put("sleep","goOutWashBaFace");
59         info.put("late","cleanTheRoom!");
60     }
61     public boolean addSay(String k,String v){
62         return info.put(k,v)==null?false:true;
63     }
64     @Override
65     public void update(Observable o,Object arg){
66             String say = info.get(arg);
67             if(say == null){
68                 return;
69             }
70             System.out.println("classHead: "+say);
71     }
72 }
73 public class ObserverDemo{
74     public static void main(String[] arguments){
75         Student tom = new Student("Tom");
76         tom.addObserver(new ClassHead());
77         tom.addObserver(new Teacher());
78 
79         System.out.println("有 "+tom.countObservers()+" 个观察者在观察Tom");
80         tom.sleep();
81         tom.late();
82     }
83 }