设计模式--享元模式

运用共享技术有效地支持大量细粒度的对象。

享元模式可以避免大量非常相似类的开销。在程序设计中，有时需要生成大量细粒度的类实例来表示数据。如果能发现这些实例除了几个参数外基本上都是相同的，有时就能够受大幅度地减少需要实例化的类的数量。

//享元类
abstract class Flyweight
{
public abstract void Use();
}

//具体实现

class ConcreteFlyweight : Flyweight
{
string name;
public ConcreteFlyweight(string name)
{
this.name = name;
}
public override void Use()
{
Console.WriteLine("具体分类：{0}", name);
}

}

//享元工厂
class FlyweightFactory
{
Hashtable flyweights = new Hashtable();

public Flyweight GetFlyweights(string key)
{
if(!flyweights.ContainsKey(key))
{
flyweights.Add(key, new ConcreteFlyweight(key));
}
return (Flyweight)flyweights[key];
}

public Flyweight GetFlyweight(string key)
{
return (Flyweight)flyweights[key];
}

public int GetCount()
{
return flyweights.Count;
}

}

调用：

FlyweightFactory f = new FlyweightFactory();

f.GetFlyweights("x").Use();
f.GetFlyweights("y").Use();
f.GetFlyweights("y").Use();
f.GetFlyweights("z").Use();

Console.WriteLine("分类总数：" + f.GetCount());