东南大学Java设计模式作业观察者模式.doc

实例一：猫、狗与老鼠 假设猫是老鼠和狗的观察目标，老鼠和狗是观察者，猫叫老鼠跑，狗也跟着叫，使用观察者模式描述该过程。类图：代码：import java.util.*;public abstract class MySubject protected ArrayList observers = new ArrayList();public abstract void attach(MyObserver obs);public abstract void detach(MyObserver obs);public abstract void cry(); public class Cat extends MySubjectpublic void attach(MyObserver obs)obs.add(obs);public void detach(MyObserver obs)obs.remove(obs);public voi