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设计模式-享元模式

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用于减少创建对象的数量，以减少内存占用和提高性能
运用共享技术有效地支持大量细粒度的对象
在有大量对象时，有可能会造成内存溢出，我们把其中共同的部分抽象出来，如果有相同的业务请求，直接返回在内存中已有的对象，避免重新创建
用 HashMap(Hashtable) 存储这些对象

string 运用了Flyweight模式

享元模式

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//Flyweight 享元接口
abstract class Flyweight
{
    public abstract void Operation(int extrinsicstate);
}
//共享的Flyweight子类
class ConcreateFlyweight : Flyweight
{
    public override void Operation(int extrinsicstate)
    {
        Console.WriteLine("具体Flayweight: " + extrinsicstate);
    }
}
//不需要共享的Flyweight子类
class UnsharedConcreateFlyweight : Flyweight
{
    public override void Operation(int extrinsicstate)
    {
        Console.WriteLine("不共享的具体Flayweight: " + extrinsicstate);
    }
}
//享元工厂
class FlyweightFactory
{
    private Hashtable flyweights = new Hashtable();
    public FlyweightFactory()
    {
        flyweights.Add("X", new ConcreateFlyweight());
        flyweights.Add("Y", new ConcreateFlyweight());
        flyweights.Add("X", new ConcreateFlyweight());
    }
    public Flyweight GetFlyweight(string key)
    {
        if(!flyweights.ContainKey(key))
            flyweights.Add(key, new ConcreateFlyweight());
        return(Flyweight)flyweight[key];
    }
}
//Client
int extrinsicstate = 22;
FlyweightFactory f = new FlyweightFactory();
Flyweight fx = f.GetFlyweight("X");
fx.Operation(--extrinsicstate);
Flyweight fy = f.GetFlyweight("Y");
fy.Operation(--extrinsicstate);
Flyweight fz = f.GetFlyweight("Z");
fz.Operation(--extrinsicstate);

Flyweight uf = new UnsharedConcreateFlyweight();
uf.Operation(--extrinsicstate);