观察者模式

观察者模式：
    观察者模式定义了对象之间的一对多依赖，这样一来当一个对象改变时，它的所有依赖者都会收到通知并自动更新。
 
        ObserverImplement类中实现一个含有SubjectImplement类的构造器用于向主题类注册，当主题实例发生改变时主题实例会执行notifyObserver（）函数通知其下面注册的观察者（调用观察者的update（）方法，所以观察者都要实现自己的update方法用于接收通知作出相应的改变）。主题实例会将注册的观察者保存在链表之中，用于之后的访问。
示例：
  1. 1 package com.renhq.subject;
2 import com.renhq.observer.Observer;
3 publicinterfaceSubject{
4 publicvoid registerObserver(Observer ob);
5 publicvoid removeObserver(Observer ob);
6 publicvoid notifyObserver(String s);
7 }

     

  1. 1 package com.renhq.observer;
2 publicinterfaceObserver{
3 publicvoid update(String s);
4 }

     

  1.  1 package com.renhq.subject;
 2 import java.util.Iterator;
 3 import java.util.LinkedList;
 4 import java.util.List;
 5 import com.renhq.observer.Observer;
 6 publicclassSubjectImplementimplementsSubject{
 7 privateList<Observer> list =newLinkedList<Observer>();
 8 @Override
 9 publicvoid registerObserver(Observer ob){
10 // TODO Auto-generated method stub
11 this.list.add(ob);
12 }
13 @Override
14 publicvoid removeObserver(Observer ob){
15 // TODO Auto-generated method stub
16 this.list.remove(ob);
17 }
18 @Override
19 publicvoid notifyObserver(String s){
20 // TODO Auto-generated method stub
21 Iterator it = list.iterator();
22 Observer ob;
23 while(it.hasNext()){
24 ob =(Observer)it.next();
25 ob.update(s);
26 }
27 }
28 publicvoid modify(String s){
29 notifyObserver(s);
30 }
31 }

     

  1.  1 package com.renhq.observer;
 2 import com.renhq.subject.Subject;
 3 publicclassObserverImplementimplementsObserver{
 4 privateSubject subject;
 5 privateString chiness;
 6 privateString en;
 7 publicObserverImplement(Subject s){
 8 // TODO Auto-generated constructor stub
 9 subject = s;
10 s.registerObserver(this);
11 }
12 @Override
13 publicvoid update(String s){
14 // TODO Auto-generated method stub
15 System.out.println(s.equals("cn")?chiness:en);
16 }
17 publicString getChiness(){
18 return chiness;
19 }
20 publicvoid setChiness(String chiness){
21 this.chiness = chiness;
22 }
23 publicString getEn(){
24 return en;
25 }
26 publicvoid setEn(String en){
27 this.en = en;
28 }
29 }

     

  1.  1 package com.renhq.subject;
 2 import com.renhq.observer.Observer;
 3 import com.renhq.observer.ObserverImplement;
 4 publicclassTest{
 5 publicstaticvoid main(String[] args){
 6 // TODO Auto-generated method stub
 7 SubjectImplement subject =newSubjectImplement();
 8 ObserverImplement observer1 =newObserverImplement(subject);
 9 ObserverImplement observer2 =newObserverImplement(subject);
10 observer1.setChiness("你好！");
11 observer1.setEn("Hello!");
12 observer2.setChiness("我是张三。");
13 observer2.setEn("I'm Zhangsan.");
14 subject.modify("en");
15 System.out.println("--------------请说人话-----------------");
16 subject.modify("cn");
17 }
18 }

     

运行结果：两个观察者都对主题的改变做出了回应
 





posted @ 2015-07-22 13:30  renhq  阅读(200)  评论(0)    收藏  举报