今日总结

观察者模式——java实现

 

问题描述：

当股票的价格上涨或下降5%时，会通知持有该股票的股民，当股民听到价格上涨的消息时会买股票，当价格下降时会大哭一场。

 

 

 

 

Java源代码：

 1 //Observer.java
 2 package shiyan21;
 3 
 4 public interface Observer {
 5     public void buy();
 6     public void cry();
 7 }  
 8 //Subject.java
 9 package shiyan21;
10 
11 import java.util.ArrayList;
12 
13 public abstract class Subject {
14     protected ArrayList<Observer> observers;
15     public Subject(){
16         observers=new ArrayList<>();
17     }
18     public void attach(Observer a){
19         observers.add(a);
20     } 
21     public void detach(Observer a){
22         observers.remove(a);
23     }
24     public abstract void up();
25     public abstract void down();
26 }
27 //Gufen.java
28 package shiyan21;
29 
30 import java.util.ArrayList;
31 public class Gufen extends Subject{
32     public void up(){
33         System.out.println("****股份上涨5%****");
34         for(Observer guan:observers){
35             guan.buy();
36             }
37     }
38     public void down(){
39         System.out.println("****股份下跌5%****");
40         for(Observer guan:observers){
41             guan.cry();
42             }
43     }
44 }
45 //Gumin.java
46 package shiyan21;
47 
48 public class Gumin implements Observer{
49     private String name;
50     public Gumin(String a){name=a;}
51     public void buy(){
52         System.out.println("股民"+name+"买了一些股票");
53     }
54     public void cry(){
55         System.out.println("股民"+name+"哭了");
56     }
57 }  
58 //main.java
59 package shiyan21;
60 public class main {
61     public static void main(String[] args) {
62         Gufen f=new Gufen();
63         Gumin g1=new Gumin("小张");
64         Gumin g2=new Gumin("小王");
65         f.attach(g1);
66         f.attach(g2);
67         f.up();
68         f.down();
69     }
70 }