程序设计: 猫大叫一声,所有的老鼠都开始逃跑,主人被惊醒。(C#语言)
要求: 1.要有联动性,老鼠和主人的行为是被动的。
2.考虑可扩展性,猫的叫声可能引起其他联动效应。
参考答案:
要点:1. 联动效果,运行代码只要执行Cat.Cryed()方法。2. 对老鼠和主人进行抽象
评分标准: <1>.构造出Cat、Mouse、Master三个类,并能使程序运行(2分)
<2>从Mouse和Master中提取抽象(5分)
<3>联动效应,只要执行Cat.Cryed()就可以使老鼠逃跑,主人惊醒。(3分)
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using System;
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using System.Collections;
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public interface Observer
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{
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void Response(); //观察者的响应,如是老鼠见到猫的反映
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}
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public interface Subject
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{
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void AimAt(Observer obs); //针对哪些观察者,这里指猫的要扑捉的对象---老鼠
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}
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public class Mouse : Observer
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{
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private string name;
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public Mouse(string name, Subject subj)
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{
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this.name = name;
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subj.AimAt(this);
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}
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public void Response()
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{
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Console.WriteLine(name + " attempt to escape!");
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}
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}
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public class Master : Observer
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{
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public Master(Subject subj)
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{
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subj.AimAt(this);
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}
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public void Response()
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{
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Console.WriteLine("Host waken!");
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}
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}
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public class Cat : Subject
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{
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private ArrayList observers;
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public Cat()
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{
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this.observers = new ArrayList();
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}
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public void AimAt(Observer obs)
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{
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this.observers.Add(obs);
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}
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public void Cry()
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{
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Console.WriteLine("Cat cryed!");
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foreach (Observer obs in this.observers)
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{
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obs.Response();
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}
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}
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}
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class MainClass
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{
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static void Main(string[] args)
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{
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Cat cat = new Cat();
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Mouse mouse1 = new Mouse("mouse1", cat);
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Mouse mouse2 = new Mouse("mouse2", cat);
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Master master = new Master(cat);
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cat.Cry();
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}
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}

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//---------------------------------------------------------------------------------------------
设计方法二: 使用event -- delegate设计..
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using System;
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public delegate void SubEventHandler();
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public abstract class Subject
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{
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public event SubEventHandler SubEvent;
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protected void FireAway()
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{
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if (this.SubEvent != null)
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this.SubEvent();
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}
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}
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public class Cat : Subject
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{
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public void Cry()
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{
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Console.WriteLine("cat cryed.");
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this.FireAway();
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}
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}
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public abstract class Observer
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{
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public Observer(Subject sub)
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{
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sub.SubEvent += new SubEventHandler(Response);
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}
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public abstract void Response();
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}
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public class Mouse : Observer
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{
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private string name;
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public Mouse(string name, Subject sub) : base(sub)
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{
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this.name = name;
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}
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public override void Response()
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{
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Console.WriteLine(name + " attempt to escape!");
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}
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}
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public class Master : Observer
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{
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public Master(Subject sub) : base(sub){}
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public override void Response()
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{
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Console.WriteLine("host waken");
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}
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}
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class Class1
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{
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static void Main(string[] args)
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{
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Cat cat = new Cat();
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Mouse mouse1 = new Mouse("mouse1", cat);
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Mouse mouse2 = new Mouse("mouse2", cat);
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Master master = new Master(cat);
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cat.Cry();
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}
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}
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-----------------
我个人倾向于 第二中方法。
终于知道怎么发 代码帖子了,以后我会多多努力的。