java 设计模式笔试题_一道java关于设计模式笔试题

题目：猫大叫一声，所有的老鼠都开始逃跑，主人被惊醒

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

两种方法

1   使用观察者模式

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();

}

}

2   使用事件

public   delegate   void   SubEventHandler();

public   abstract   class   Subject

{

public   event   SubEventHandler   SubEvent;

protected   void   FireAway()

{

if   (this.SubEvent   !=   null)

this.SubEvent();

}

}

public   class   Cat   :   Subject

{

public   void   Cry()

{

Console.WriteLine("cat   cryed.");

this.FireAway();

}

}

public   abstract   class   Observer

{

public   Observer(Subject   sub)

{

sub.SubEvent   +=   new   SubEventHandler(Response);

}

public   abstract   void   Response();

}

public   class   Mouse   :   Observer

{

private   string   name;

public   Mouse(string   name,   Subject   sub)   :   base(sub)

{

this.name   =   name;

}

public   override   void   Response()

{

Console.WriteLine(name   +   "   attempt   to   escape!");

}

}

public   class   Master   :   Observer

{

public   Master(Subject   sub)   :   base(sub){}

public   override   void   Response()

{

Console.WriteLine("host   waken");

}

}

class   Class1

{

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();

}

}