观察者模式

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;


public class client {
    public static void main(String[] args) {
        // 人民日报开通公众号
        WeChatSubscribe peopleDaily = new PeopleDaily();
        //关注订阅
        peopleDaily.add(new ZhangSan());
        peopleDaily.add(new LiSi());
        peopleDaily.sendMessage = "hhh";
        peopleDaily.notifyObserver();
    }
}

// 抽象主题
abstract class WeChatSubscribe {
    // 定义观察者集合
    protected List<AbstractOB> observers = new ArrayList<AbstractOB>();

    public String sendMessage = "";

    // 添加观察者方法
    public void add(AbstractOB observer) {
        observers.add(observer);
    }

    // 移出观察者方法
    public void remove(AbstractOB observer) {
        Iterator<AbstractOB> iterator = observers.iterator();
        while (iterator.hasNext()) {
            AbstractOB next = iterator.next();
            if (next == observer) {
                iterator.remove();
            }
        }
//        observers.remove(observer);
    }

    // 发送消息的行为
    public abstract void notifyObserver();
}

// 抽象观察者
abstract class AbstractOB {
    abstract void response(WeChatSubscribe subscribe);
}

// 具体目标
class PeopleDaily extends WeChatSubscribe {

    @Override
    public void notifyObserver() {
        System.out.println("今天是雨天" + sendMessage);
        for (AbstractOB ob : observers) {
            ob.response(this);
        }
    }
}

// 具体目标2
//class BJ extends WeChatSubscribe{}


//具体观察者1-张三
class ZhangSan extends AbstractOB {
    public void response(WeChatSubscribe subscribe) {
        System.out.println("张三作为具体观察者，听了很伤心");
    }
}

//具体观察者2-李四
class LiSi extends AbstractOB {
    public void response(WeChatSubscribe subscribe) {
        System.out.println("李四作为具体观察者，听了很高兴");
        //取下观察
        System.out.println("当前的订阅人数" + subscribe.observers.size());
        subscribe.remove(this);
        System.out.println("移除后订阅人数" + subscribe.observers.size());
    }
}