享元模式

//抽象享元角色
public abstract class Flyweight{
	//内部状态
	private String intrinsic;
	//外部状态
	private final String Extrinsic;  //将外部状态定义为final，是为了防止意外产生，防止无意中修改导致池混乱
	/*
		注意：在程序开发中，确认只需要一次赋值的属性则设置为final类型，避免无意修改导致逻辑混乱，特别是Session
		级的常量或变量
	*/
	//要求享元角色必须接受外部状态
	public Flyweight(String _extrinsic){
		this.Extrinsic=_extrinsic;
	}
	//定义业务操作
	public abstract void operate();
	//内部状体的getter/setter
	public String getIntrinsic(){
		return intrinsic;
	}
	public void setIntrinsic(String intrinsic){
		this.intrinsic=intrinsic;
	}
}

//具体享元角色
public class ConcreteFlyweight1 extends Flyweight{
	//接受外部状态
	public ConcreteFlyweight1(String _extrinsic){
		super(_extrinsic);
	}
	//根据外部状体进行逻辑处理
	public void operate(){
	
	}
}
public class ConcreteFlyweight2 extends Flyweight{
	//接受外部状态
	public ConcreteFlyweight2(String _extrinsic){
		super(_extrinsic);
	}
	//根据外部状体进行逻辑处理
	public void operate(){
	
	}
}

//享元工厂
public class FlyweightFactory{
	//定义一个池容量
	private static HashMap<String,Flyweight> pool=new HashMap<String,Flyweight>();
	//享元工厂
	public static Flyweight getFlyweight(String extrinsic){
		//需要返回的对象
		Flyweight flyweight=null;
		//在池中没有该对象
		if(pool.containKey(extrinsic)){
			flyweight=pool.get(extrinsic);
		}else{
			//根据外部状态创建享元对象
			flyweight=new ConcreteFlyweight1(extrinsic);
			//放置到池中
			pool.put(extrinsic,flyweight);
		}
		return flyweight;
	}
}