方式三：更具备通用性，添加监听事件（让多个人同时监听小孩醒来这个事件并作出相应动作，dad和mom就是观察者）

class Dad implements WakeUpActionListener{
	@Override
	public void wakeUpAction(WakeUpEvent wakeUpEvent)
	{
		System.out.println("爸爸给小孩喂奶。。。");
		
	}
}
class Mom implements WakeUpActionListener{

	@Override
	public void wakeUpAction(WakeUpEvent wakeUpEvent)
	{
		System.out.println("妈妈给小孩喂奶");
		
	}
	
}
class WakeUpEvent{
	
}
interface WakeUpActionListener{
	 void wakeUpAction(WakeUpEvent wakeUpEvent);
}
class Child implements Runnable{
	private List<WakeUpActionListener> listenerLists=new ArrayList<WakeUpActionListener>();
	 void addListener(WakeUpActionListener l){
		listenerLists.add(l);
	}
	 void wakeUp(){
		 System.out.println("醒来了");
		 for(WakeUpActionListener l:listenerLists){
			 l.wakeUpAction(new WakeUpEvent());
		 }
	 }
	@Override
	public void run()
	{
		try
		{
			Thread.sleep(5000);
		} catch (InterruptedException e)
		{
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		wakeUp();
		
	}
}
public class Test
{
	public static void main(String[] args){
		Dad d=new Dad();
		Mom m=new Mom();
		Child c=new Child();
		c.addListener(d);
		c.addListener(m);
		new Thread(c).start();
	}
}

用属性文件管理Observers

将上面代码部分的main函数换成以下

	public static void main(String[] args) throws IOException, InstantiationException, IllegalAccessException, ClassNotFoundException{
		Child c=new Child();
		Properties props=new Properties();
		//如果文件放在src下直接可以写文件名，如果放在包下写上路径
		props.load(Test.class.getClassLoader().getResourceAsStream("ObserverMode/observer.properties"));
		String[] observers=props.getProperty("observers").split(",");
		for(String observer:observers){
			c.addListener((WakeUpActionListener)Class.forName(observer).newInstance());
		}
		new Thread(c).start();
	}

Obverser观察者模式二

原文：http://blog.csdn.net/jcy472578/article/details/18603289