面向对象的设计模式 ——享元模式

享元模式：就是提前的申请资源备用，当多个地方要重复使用这个实例是就直接拿出来用，而不是从新new

当程序多个地方都要用到这个类，而这个类那么就把这个类的参数移出来，重新抽象一个类，就可以省内存了

这个模式往往要大量的重复实例才会用到。

面向对象的设计模式 ——享元模式

abstract class Flyweight{
    public abstract void Operation(int extrinsicstate);
}

class ConcreteFlyweight extends Flyweight{
    public void Operation(int extrinsicstate){
        System.out.println("具体Flyweight"+extrinsicstate);
    }
}

class UnshareConcreteFlyweight extends Flyweight{
    public void Operation(int extrinsicstate){
        System.out.println("不共享的具体Flyweight:"+extrimsicstate);
    }
}

class FlyweightFactory{
    private hashMap<Flyweight> flyweights = new hashMap<Flyweight>;
    
    public FlyweightFactory(){
        flyweights.add("X",new ConcreteFlyweight());
        flyweights.add("Y",new ConcreteFlyweight());
        flyweights.add("Z",new ConcreteFlyweight());
    } 

    public Flyweight getFlyweight(String key){
        return ((Flyweight)flyweights.get("X"));
    }
}

public class Test{
    int extrinsicstate = 22;
    
    FlyweightFactory f = new FlyweightFactory();

    Flyweight fx = f.GetFlyweight("X");
    fx.Operation(--extrinsicstate);

    Flyweight fy = f.GetFlyweight("Y");
    fx.Operation(--extrinsicstate);

    Flyweight fz = f.GetFlyweight("Z");
    fx.Operation(--extrinsicstate);

    UnsharedConcreteFlyweight uf = new UnsharedConcreteFlyweight();

    uf.Operation(--extrinsicstate);
}