设计模式行为型模式观察者模式

描述

观察者模式又叫发布订阅模式,拥有一个监听者,如果一个被监听者发生了改变则会通知到所有监听者。例子,警察和嫌疑犯之间就是观察者模式。微信朋友圈,相对于好友,你就是观察者,微信好友发送朋友圈你会收到通知

类图

代码实现

public class PoliceMan {
    private String name;

    public PoliceMan(String name) {
        this.name = name;
    }

    public void name() {
        System.out.println("我是:" + name + "收到消息");
    }

}

public class XianFan1 {
    private String name;

    public XianFan1(String name) {
        this.name = name;
    }

    private List<PoliceMan> policeManList = new ArrayList<>();

    public void addPolice(PoliceMan policeMan) {
        if (!policeManList.contains(policeMan)) {
            policeManList.add(policeMan);
        }
    }

    public void run() {
        System.out.println(name + "跑了");
        notifyAllPoliceMan();
    }
    public void notifyAllPoliceMan(){
        policeManList.stream().forEach(i -> i.name());
    }

}

测试类

public class Main {
    public static void main(String[] args) {
        PoliceMan policeManA =new PoliceMan("警察:A");
        PoliceMan policeManB =new PoliceMan("警察:B");
        PoliceMan policeManC =new PoliceMan("警察:C");
        XianFan1 xianFan1 =new XianFan1("嫌犯1");
        xianFan1.addPolice(policeManA);
        xianFan1.addPolice(policeManB);
        xianFan1.addPolice(policeManC);
        xianFan1.run();
    }
}