设计模式——享元模式

1 简介

享元模式（Flyweight Pattern）定义：运用共享技术有效地支持大量细粒度对象的复用。系统只是用少量的对象而这些对象都很相似，状态变化很小，可以实现对象的多次复用。

2 代码

（1）抽象享元类（Flyweight）

public interface Flyweight { public void operation(String extrinsicState); }

（2）具体享元类（ConcreteFlyweight）

public class ConcreteFlyweight implements Flyweight{ private String instrinsicState; @Override public void operation(String extrinsicState) { } }

（3）非共享具体享元类（UnsharedConcreteFlyweight）

public class UnsharedConcreteFlyweight implements Flyweight{ private String allState; @Override public void operation(String extrinsicState) { } }

（4）享元工厂（FlyweightFactory）

import java.util.HashMap; public class FlyweightFactory { private HashMap<String,Flyweight> flyweights=new HashMap<String,Flyweight>(); public Flyweight getFlyweight(String key) { if(flyweights.containsKey(key)) { return flyweights.get(key); }else { Flyweight fw=new ConcreteFlyweight(); flyweights.put(key, fw); return fw; } } }