猫叫老鼠跑-观察者模式

　　当一个对象的状态发生改变时，他的所有依赖者都会收到通知并自动更新---------观察者模式

　　即，猫A发出了叫声，老鼠B(老鼠C,D,E,F...)听到了这个声音，立即掉头就跑.

package ares.core;

import java.util.ArrayList;

public class Cat implements Subject {
    private ArrayList<Observer> observers = new ArrayList<Observer>();
    private String name;

    public Cat(String name) {
        this.name = name;
    }
    
    public String getName() {
        return this.name;
    }

    @Override
    public void register(Observer o) {
        observers.add(o);
    }

    @Override
    public void remove(Observer o) {
        if (observers != null && observers.size() > 0) {
            int index = observers.indexOf(o);
            if (index >= 0) {
                observers.remove(index);
            }
        }
    }

    @Override
    public void notifyObserver() {
        for (Observer observer : observers) {
            observer.listen();
        }
    }

    public void shout() {
        System.out.println(this.name+":喵~喵~");
        notifyObserver();
    }

}

package ares.core;

public interface Subject {
    public void register(Observer o);

    public void remove(Observer o);

    public void notifyObserver();
}

package ares.core;

public class Mouse implements Observer {
    private Cat cat;
    private String name;

    Mouse(String name, Cat cat) {
        this.name = name;
        this.cat = cat;
        cat.register(this);
    }

    @Override
    public void listen() {
        System.out.println(this.name + "听见"+cat.getName()+"叫!");
        run();
    }

    public void run() {
        System.out.println(this.name + ":"+cat.getName()+"来了，兄弟们快跑");
    }

}

package ares.core;

public interface Observer {
    public void listen();
}

package ares.core;

public class Main {

    public static void main(String[] args) {
        Cat cat = new Cat("大洋芋");
        Mouse mouse=new Mouse("小米渣", cat);
        cat.shout();
    }

}