package observerForJDK;import java.util.Observable;/*** 新闻派发器，当有新的新闻时派发给所有的订阅读者(观察者)*/
public class NewsDispatcher extends Observable {public void addNews(String news){this.setChanged();this.notifyObservers(news);}
}

package observerForJDK;import java.util.Observable;
import java.util.Observer;/*** 读者（观察者）*/
public class Reader implements Observer {private String name;public Reader(String name) {this.name = name;}public void update(Observable o, Object arg) {String news = (String)arg;System.out.println(name + "观察到 : " + news);}
}

package observerForJDK;/*** 测试类*/
public class app {public static void main(String[] args) {//体育新闻派发器NewsDispatcher sportNewsDispatcher = new NewsDispatcher();//it新闻派发器NewsDispatcher itNewsDispatcher = new NewsDispatcher();//观察者r1,r2,r3Reader r1 = new Reader("r1");Reader r2 = new Reader("r2");Reader r3 = new Reader("r3");//添加观察者
        sportNewsDispatcher.addObserver(r1);sportNewsDispatcher.addObserver(r2);itNewsDispatcher.addObserver(r3);//当有新的新闻的时候，通知观察者sportNewsDispatcher.addNews("中国队突破了历史获得了世界杯冠军!");itNewsDispatcher.addNews("ibm 收购 sun公司，java开始收费!");}
}

package observerForJDK;import java.util.Observable;
import java.util.Observer;/*** 读者（观察者）*/
public class Reader2 implements Observer {private String name;private Observable observable;public Reader2(Observable observable,String name) {this.observable = observable;this.observable.addObserver(this);this.name = name;}public void update(Observable o, Object arg) {String news = (String)arg;System.out.println(name + "观察到 : " + news);}
}

package observerForJDK;/****/
public class app2 {public static void main(String[] args) {//体育新闻派发器NewsDispatcher sportNewsDispatcher = new NewsDispatcher();//it新闻派发器NewsDispatcher itNewsDispatcher = new NewsDispatcher();//观察者r1,r2,r3Reader2 r1 = new Reader2(sportNewsDispatcher,"r1");Reader2 r2 = new Reader2(sportNewsDispatcher,"r2");Reader2 r3 = new Reader2(itNewsDispatcher,"r3");//当有新的新闻的时候，通知观察者sportNewsDispatcher.addNews("中国队突破了历史获得了世界杯冠军!");itNewsDispatcher.addNews("ibm 收购 sun公司，java开始收费!");}
}

//读者类，要实现观察者接口
public class Reader implements Observer{private String name;public Reader(String name) {super();this.name = name;}public String getName() {return name;}//读者可以关注某一位作者，关注则代表把自己加到作者的观察者列表里public void subscribe(String writerName){WriterManager.getInstance().getWriter(writerName).addObserver(this);}//读者可以取消关注某一位作者，取消关注则代表把自己从作者的观察者列表里删除public void unsubscribe(String writerName){WriterManager.getInstance().getWriter(writerName).deleteObserver(this);}//当关注的作者发表新小说时，会通知读者去看public void update(Observable o, Object obj) {if (o instanceof Writer) {Writer writer = (Writer) o;System.out.println(name+"知道" + writer.getName() + "发布了新书《" + writer.getLastNovel() + "》，非要去看！");}}}

//作者类，要继承自被观察者类
public class Writer extends Observable{private String name;//作者的名称private String lastNovel;//记录作者最新发布的小说public Writer(String name) {super();this.name = name;WriterManager.getInstance().add(this);}//作者发布新小说了，要通知所有关注自己的读者public void addNovel(String novel) {System.out.println(name + "发布了新书《" + novel + "》！");lastNovel = novel;setChanged();notifyObservers();}public String getLastNovel() {return lastNovel;}public String getName() {return name;}}

import java.util.HashMap;
import java.util.Map;//管理器，保持一份独有的作者列表
public class WriterManager{private Map<String, Writer> writerMap = new HashMap<String, Writer>();//添加作者public void add(Writer writer){writerMap.put(writer.getName(), writer);}//根据作者姓名获取作者public Writer getWriter(String name){return writerMap.get(name);}//单例private WriterManager(){}public static WriterManager getInstance(){return WriterManagerInstance.instance;}private static class WriterManagerInstance{private static WriterManager instance = new WriterManager();}
}

//客户端调用
public class Client {public static void main(String[] args) {//假设四个读者，两个作者Reader r1 = new Reader("谢广坤");Reader r2 = new Reader("赵四");Reader r3 = new Reader("七哥");Reader r4 = new Reader("刘能");Writer w1 = new Writer("谢大脚");Writer w2 = new Writer("王小蒙");//四人关注了谢大脚r1.subscribe("谢大脚");r2.subscribe("谢大脚");r3.subscribe("谢大脚");r4.subscribe("谢大脚");//七哥和刘能还关注了王小蒙r3.subscribe("王小蒙");r4.subscribe("王小蒙");//作者发布新书就会通知关注的读者//谢大脚写了设计模式w1.addNovel("设计模式");//王小蒙写了JAVA编程思想w2.addNovel("JAVA编程思想");//谢广坤取消关注谢大脚r1.unsubscribe("谢大脚");//谢大脚再写书将不会通知谢广坤w1.addNovel("观察者模式");}}