享元模式：运用共享技术有效地支持大量细粒度的对象。

适用场合：假设一个应用程序适用了大量的对象。而大量的这些对象造成了非常大的存储开销时就应该考虑使用。

首先定义一个IFlyweight接口

public interface IFlyweight {

    public void operation(int extrinsicstate);

}

接着定义一个ConcreteFlyweight继承IFlyweight

public class ConcreteFlyweight implements IFlyweight{

    @Override

    public void operation(int extrinsicstate) {

        System.out.println("详细flyweight:"+extrinsicstate);

    }

}

再定义一个UnsharedConcreteFlyweight继承IFlyweight

public class UnsharedConcreteFlyweight implements IFlyweight{

    @Override

    public void operation(int extrinsicstate) {

        System.out.println("不共享的详细flyweight:"+extrinsicstate);

    }

}

然后定义一个FlyweightFactory

public class FlyweightFactory {

    Map<String, IFlyweight> flyweights=new HashMap<String,IFlyweight>();

    public FlyweightFactory(){

        flyweights.put("x", new ConcreteFlyweight());

        flyweights.put("y", new ConcreteFlyweight());

        flyweights.put("z", new ConcreteFlyweight());

    }

    public IFlyweight getFlyweight(String key){

        return flyweights.get(key);

    }

}

client代码

public static void main(String[] args) {

        //享元模式

        int extrinsicstate=22;

        FlyweightFactory factory=new FlyweightFactory();

        IFlyweight fx=factory.getFlyweight("x");

        fx.operation(--extrinsicstate);

        IFlyweight fy=factory.getFlyweight("y");

        fy.operation(--extrinsicstate);

        IFlyweight fz=factory.getFlyweight("z");

        fz.operation(--extrinsicstate);

        IFlyweight uf=new UnsharedConcreteFlyweight();

        uf.operation(--extrinsicstate);

    }