定义:使用共享对象可以有效的支持大量的细粒度的对象
FlyWeight抽象享元类:通常是一个接口或抽象类,声明公共方法,这些方法可以向外界提供对象的内部状态,设置外部状态。
UnsharedConcreteFlyWeight非共享享元类:不能被共享的子类可以设计为非共享享元类。
ConcreteFlyWeight具体享元类:为内部状态提供成员变量进行存储。
FlyWeightFactory享元工厂类:创建并管理享元对象,享元池一般设计为键值对。
//抽象享元类
abstract class Flyweight {
private String intrinsic;
protected final String Extrinsic;
public Flyweight(String Extrinsic){
this.Extrinsic = Extrinsic;
}
public abstract void operate();
public String getIntrinsic(){
return intrinsic;
}
public void setIntrinsic(String intrinsic){
this.intrinsic = intrinsic;
}
}
//具体享元类
class ConcreteFlyweight1 extends Flyweight{
public ConcreteFlyweight1(String Extrinsic) {
super(Extrinsic);
}
@Override
public void operate() {
}
}
//享元工厂
class FlyweightFactory {
//对象池
private static HashMap<String,Flyweight> pool = new HashMap<>();
public static Flyweight getFlyweight(String Extrinsic){
Flyweight flyweight = null;
if(pool.containsKey(Extrinsic))
flyweight = pool.get(Extrinsic);
else {
flyweight = new ConcreteFlyweight1(Extrinsic);
pool.put(Extrinsic, flyweight);
}
return flyweight;
}
}
优缺点:
减少对象的创建,减少内存占用
增加系统复杂度
使用场景
系统中存在大量相似对象
缓冲对象池
注意事项
多线程问题