//Observable是被觀察者對(duì)象接口，實(shí)現(xiàn)該接口就是：目標(biāo)（被觀察者）的具體實(shí)現(xiàn)
public class TargetObservable extends Observable {
 // 要觀察的數(shù)據(jù)：消息發(fā)生改變時(shí)，所有被添加的觀察者都能收到通知
 private String message;
 public String getConent() {
  return message;
 }
 public void setMessage(String message) {
  this.message = message;
  // 被觀察者數(shù)據(jù)發(fā)生變化時(shí)，通過以下兩行代碼通知所有的觀察者
  this.setChanged();
  this.notifyObservers(message);
 }
}

//Observer對(duì)象是觀察者，實(shí)現(xiàn)Observer的對(duì)象就是具體的觀察者對(duì)象
public class TargetObserver implements Observer {
 // 定義觀察者名稱
 private String name;
 public String getObserverName() {
  return name;
 }
 public void setObserverName(String observerName) {
  this.name = observerName;
 }
 @Override
 public void update(Observable arg0, Object arg1) {
  //更新消息數(shù)據(jù)
  System.out.println(name + "收到了發(fā)生變化的數(shù)據(jù)內(nèi)容是："
    + ((TargetObservable) arg0).getConent());
 }
}

public class TargetObserver01 implements Observer {
 // 定義觀察者名稱
 private String name01;
 public String getObserverName() {
  return name01;
 }
 public void setObserverName(String observerName) {
  this.name01 = observerName;
 }
 @Override
 public void update(Observable arg0, Object arg1) {
  //更新消息數(shù)據(jù)
  System.out.println(name01 + "收到了發(fā)生變化的數(shù)據(jù)內(nèi)容是："
    + ((TargetObservable) arg0).getConent());
 }
}

/**
  * @description：測試類
  * @author ldm
  * @date 2016-11-1 上午8:29:07
  */
 public static void main(String[] args) {
  // 創(chuàng)建一個(gè)具體的被 觀察者
  TargetObservable observable = new TargetObservable();
  // 創(chuàng)建第一個(gè)觀察者
  TargetObserver one = new TargetObserver();
  one.setObserverName("我是觀察者A");
  // 創(chuàng)建第二個(gè)觀察者
  TargetObserver01 two = new TargetObserver01();
  two.setObserverName("我是觀察者B");
  // 注冊觀察者
  observable.addObserver(one);
  observable.addObserver(two);
  // 目標(biāo)更新天氣情況
  observable.setMessage("***我要更新的數(shù)據(jù)***");
 }
}

我是觀察者B收到了發(fā)生變化的數(shù)據(jù)內(nèi)容是：—–我要更新的數(shù)據(jù)—–
我是觀察者A收到了發(fā)生變化的數(shù)據(jù)內(nèi)容是：—–我要更新的數(shù)據(jù)—–

package java.util;
import java.util.Observable;
public interface Observer {
 void update(Observable var1, Object var2);
}

package java.util;
import java.util.Observer;
import java.util.Vector;
public class Observable {
 private boolean changed = false;
 private Vector<Observer> obs = new Vector();
 public Observable() {
 }
 public synchronized void addObserver(Observer var1) {
  if(var1 == null) {
   throw new NullPointerException();
  } else {
   if(!this.obs.contains(var1)) {
    this.obs.addElement(var1);
   }
  }
 }
 public synchronized void deleteObserver(Observer var1) {
  this.obs.removeElement(var1);
 }
 public void notifyObservers() {
  this.notifyObservers((Object)null);
 }
 public void notifyObservers(Object var1) {
  Object[] var2;
  synchronized(this) {
   if(!this.changed) {
    return;
   }
   var2 = this.obs.toArray();
   this.clearChanged();
  }
  for(int var3 = var2.length - 1; var3 >= 0; --var3) {
   ((Observer)var2[var3]).update(this, var1);
  }
 }
 public synchronized void deleteObservers() {
  this.obs.removeAllElements();
 }
 protected synchronized void setChanged() {
  this.changed = true;
 }
 protected synchronized void clearChanged() {
  this.changed = false;
 }
 public synchronized boolean hasChanged() {
  return this.changed;
 }
 public synchronized int countObservers() {
  return this.obs.size();
 }
}