我理解的观察者模式

观察者模式避免了各组件之间紧密耦合，它将观察者和被观察的对象分离开来，一个对象添加一个方法（即观察者注册自己）使本身变得可观察，当可观察的对象更改时，它会将消息发送到已注册的观察者，这些观察者收到消息后执行的操作与可观察的对象无关，这种模式使得对象之间可以相互对话，而不用了解原因；

下面我们来看一个列子

package com.ys.observer;

import java.util.ArrayList;

/**
 * 利用观察者模式实现一个天气预报,当天气发生更改时，通知观察者
 * @author cena
 *
 */
interface Weather{
	public void  registObserver(Observer observer);
	public void  removeObserver(Observer observer);
	public void  notiyAll();
}

interface Observer{
	public void update(int t);
}

class WeatherImpl implements Weather{
	ArrayList<Observer>list=new ArrayList<Observer>();
	private int temperature;
	@Override
	public void registObserver(Observer observer) {
		list.add(observer);
	}

	@Override
	public void removeObserver(Observer observer) {
		list.remove(observer);
	}

	@Override
	public void notiyAll() {
		for (int i = 0; i < list.size(); i++) {
			list.get(i).update(temperature);
		}
	}
	public void setTemperature(int n) {
		this.temperature=n;
		notiyAll();
	}
	public int getTemperature() {
		return temperature;
	}
}

class OberverImpl01 implements Observer {

	private int temperature;
	public OberverImpl01(Weather weather) {
		weather.registObserver(this);
	}
	public void update(int t) {
		this.temperature=t;
		disPlay();
	}
	public void disPlay() {
		System.out.println("01temperature is "+temperature);
	}
}
class OberverImpl02 implements Observer {

	private int temperature;
	public OberverImpl02(Weather weather) {
		weather.registObserver(this);
	}
       @Override
	public void update(int t) {
		this.temperature=t;
		disPlay();
	}
	public void disPlay() {
		System.out.println("02temperature is "+temperature);
	}
}
public class Test {	
	public static void main(String[] args) {
		WeatherImpl weather=new WeatherImpl();
		Observer observer01=new OberverImpl01(weather);
		Observer observer02=new OberverImpl02(weather);
		weather.setTemperature(28);
	}
}