标签：style blog http color io 使用 java ar for
享元模式(Flyweight Pattern)，Flyweight在拳击比赛中是最轻量级别--蝇量级。享元模式以共享的方式支持大量的细粒度对象。
享元模式在编辑系统中被大量使用，例如字母a会在许多的地方出现，尽管所出现的位置和字模风格不尽相同，但是都可以共享一个字母a的对象。
Java中的String是final的，改变String的内容就是一个新的String了。只要是内容相同，多个String对象是可以共享一个String实例的。
享元模式可以分为单纯享元模式和复合享元模式两种。
单纯享元模式中，所有享元对象都是可以共享的。下面是单纯享元模式的类图：
核心是FlyweightFactory，采取的是登记的工厂方式，用HashMap存储已经构造的ConcreteFlyweight。调用时先去查看HashMap是否已经存在，已存在则直接调用。不存在时先创建再添加到HashMap中以共享使用。
Flyweight接口的示例代码：
public abstract class Flyweight{ public abstract void operation(String state); }
具体类ConcreteFlyweight的示例代码：
public class ConcreteFlyweight extends Flyweight{ private Character intrinsicState = null; public ConcreteFlyweight(Character state){ this.intrinsicState = state; } public void operation(String state){ System.out.print( "\nIntrinsic State = " + intrinsicState + ", Extrinsic State = " + state); } }
工厂类FlyweightFactory的示例代码：
public class FlyweightFactory{ private HashMap flies = new HashMap(); private Flyweight lnkFlyweight; public FlyweightFactory(){ } public synchronized Flyweight factory(Character state){ if (flies.containsKey(state)){ return (Flyweight)flies.get(state); } else{ Flyweight fly = new ConcreteFlyweight(state); flies.put(state, fly); return fly; } } public void checkFlyweight(){ Flyweight fly ; int i = 0; System.out.println("\n==========checkFlyweight()============="); for (Iterator it = flies.entrySet().iterator() ; it.hasNext(); ){ Map.Entry e = (Map.Entry) it.next(); System.out.println("Item " + (++i) + " : " + e.getKey()); } System.out.println("==========checkFlyweight()============="); } }
客户端client的示例代码：
public class Client{ private static FlyweightFactory factory; public static void main(String[] args){ factory = new FlyweightFactory(); Flyweight fly = factory.factory(new Character(‘a‘)); fly.operation("First Call"); fly = factory.factory(new Character(‘b‘)); fly.operation("Second Call"); fly = factory.factory(new Character(‘a‘)); fly.operation("Third Call"); // intrinsic Flyweight factory.checkFlyweight(); } }
客户端client在创建2个对象”a”时实际上是共享了一个对象。
标签：style blog http color io 使用 java ar for
原文地址：http://www.cnblogs.com/lnlvinso/p/3952483.html
