享元模式(Flyweight Pattern)就是通过共享技术实现大量细粒度对象的复用。享元模式是通过细粒度对象的共享,所以也可以说享元模式是一种轻量级模式。按照Gof模式分类,享元模式属于对象结构型模式。
享元模式包括下面角色
享元模式的核心在享元工厂类,享元工厂类的作用在与维护享元池,需要什么对象,可以从享元池获取
例子来自:《设计模式》一书
public class Flyweight
{
//内部状态作为成员属性
private String intrinsicState;
public Flyweight(String intrinsicState)
{
this.intrinsicState = intrinsicState;
}
public void operation(String extrinsicState)
{
......
}
}
public class FlyweightFactory
{
private HashMap flyweights = new HashMap();
public Flyweight getFlyweight(String key)
{
if(flyweights.containsKey(key))
{
//享元池有对象,直接获取
return (Flyweight)flyweights.get(key);
}
else
{
//创建具体的享元对象,存储在享元池
Flyweight fw = new ConcreteFlyweight();
flyweights.put(key,fw);
return fw;
}
}
}
享元模式分为单存享元模式和复合享元模式
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