题目：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
设计方法一:
public interface Observer 
{ 
void Response(); //观察者的响应，如是老鼠见到猫的反映 
} public interface Subject { void AimAt(Observer obs); //针对哪些观察者，这里指猫的要扑捉的对象---老鼠 } public class Mouse : Observer { private string name; public Mouse(string name, Subject subj) 
{ this.name = name; subj.AimAt(this); 
} public void Response() { Console.WriteLine(name + " attempt to escape!"); } } public class Master : Observer { public Master(Subject subj) { subj.AimAt(this); } public void Response() { Console.WriteLine("Host waken!"); } } public class Cat : Subject { private ArrayList observers; public Cat() { this.observers = new ArrayList(); } public void AimAt(Observer obs) { this.observers.Add(obs); } public void Cry() { Console.WriteLine("Cat cryed!"); foreach (Observer obs in this.observers) { obs.Response(); } } } class MainClass { static void Main(string[] args) { Cat cat = new Cat(); Mouse mouse1 = new Mouse("mouse1", cat); Mouse mouse2 = new Mouse("mouse2", cat); Master master = new Master(cat); cat.Cry(); } } 设计方法二: 使用event -- delegate设计
class Class1 { static void Main(string[] args) { Cat cat = new Cat(); Mouse mouse = new Mouse(cat); Master master = new Master(cat); cat.Cry(); Console.ReadLine(); } } public delegate void SubEventHandle(); public class SubObject { public event SubEventHandle SubEvent; public void FireEvent() { this.SubEvent(); } } public class Cat : SubObject { public void Cry() { Console.Write("Cat Cries."); this.FireEvent(); } } public abstract class Observer { public Observer(SubObject subObj) { subObj.SubEvent += new SubEventHandle(Response); } public abstract void Response(); } public class Mouse : Observer { public Mouse(SubObject subObj) : base(subObj) { } public override void Response() { Console.Write("Mouse escapes."); } } public class Master : Observer { public Master(Cat cat) : base(cat) { } public override void Response() { Console.Write("Master Weaks."); } } 2、以下输出结果？
public class A { public virtual void Fun1(int i) { Console.WriteLine(i); } public void Fun2(A a) { a.Fun1(1); Fun1(5); } } public class B : A { public override void Fun1(int i) { base.Fun1(i + 1); } public static void Main() { B b = new B(); A a = new A(); a.Fun2(b); b.Fun2(a); Console.ReadLine(); } } 答案：
2
5
1
6
3、以下输出结果？
using System; using System.Collections.Generic; using System.Text; namespace ConsoleApplication1 { public class Program { static void Main(string[] args) { test t1 = new test(); test t2 = new test(); Console.Write(t2.Count); Console.ReadLine(); } } public class test { static int count = 0; static test() { count++; } public test() { count++; } public int Count { get { return count; } } }} 答案：3