参考资料
《设计模式：可复用面向对象软件的基础》
标签：exist 实例 面向 public numbers enable sign actor gpo
享元模式（Flyweight Pattern）
The flyweight design pattern enables use sharing of objects to support large numbers of fine-grained objects efficiently.
1、Flyweight
-描述一个接口，通过这个接口flyweight可以接受并作用于外部状态。
2、ConcreteFlyweight
-实现Flyweight接口，并为内部状态（如果有的话）增加存储空间。ConcreteFlyweight对象必须是可共享的。它所存储的状态必须是内部的；即，它必须独立于ConcreteFlyweight对象的场景。
3、UnsharedConcreteFlyweight
-并非所有的Flyweight子类都需要被共享。Flyweight接口使共享成为可能，但它并不强制共享。在Flyweight对象结构的某些层次，UnsharedConcreteFlyweight对象通常将ConcreteFlyweight对象作为子节点。
4、FlyweightFactory
-创建并管理flyweight对象。
-确保合理地共享flyweight。当用户请求一个flyweight时，FlyweightFactory对象提供一个已创建的实例或创建一个。
5、Client
-维持一个对flyweight的引用。
-计算或者存储一个（多个）flyweight的外部状态。
class UnsharedConcreteFlyweight { private String sharedInfo; UnsharedConcreteFlyweight(String sharedInfo) { this.sharedInfo= sharedInfo; } public String getSharedInfo() { return sharedInfo; } public void setSharedInfo(String sharedInfo) { this.sharedInfo=sharedInfo; } }
interface Flyweight { public void operation(UnsharedConcreteFlyweight state); }
class ConcreteFlyweight implements Flyweight { private String key; ConcreteFlyweight(String key) { this.key=key; } public void operation(UnsharedConcreteFlyweight outState) { outState.getSharedInfo() } }
class FlyweightFactory { private HashMap<String, Flyweight> flyweights=new HashMap<String, Flyweight>(); public Flyweight getFlyweight(String key) { Flyweight flyweight=(Flyweight)flyweights.get(key); if(flyweight!=null) { System.out.println(key+" is exist!"); } else { flyweight=new ConcreteFlyweight(key); flyweights.put(key, flyweight); } return flyweight; } }
JAVA 中的 String，如果有则返回，如果没有则创建一个字符串保存在字符串缓存池里面。
《设计模式：可复用面向对象软件的基础》
标签：exist 实例 面向 public numbers enable sign actor gpo
原文地址：https://www.cnblogs.com/diameter/p/13194490.html
