设计模式：23、享元模式

目录

0、定义

1、享元模式的三种角色

2、享元模式的UML类图

3、示例代码

---

0、定义

        运营共享技术有效地支持大量细粒度的对象

1、享元模式的三种角色

• 享元接口（Flyweight）：是一个接口，该接口定义了享元对外公开其内部数据的方法，以及享元接收外部数据的方法。
• 具体享元（Concrete Flyweight）：实现享元接口的类。
• 享元工厂（Flyweight Factory）：享元工厂是一个类，该类的实例负责创建和管理享元对象，用户或其他对象必须请求享元工厂为它得到一个享元对象。

2、享元模式的UML类图

3、示例代码

享元接口

package xyz.jangle.design.flyweight;

public interface Flyweight {
	public void operation(int extrinsicState);
}

具体享元

package xyz.jangle.design.flyweight;

public class ConcreteFlyweight implements Flyweight {
	
	private int intrinsicState;

	public ConcreteFlyweight(int intrinsic) {
		super();
		this.intrinsicState = intrinsic;
	}

	@Override
	public void operation(int extrinsicState) {
		System.out.println(intrinsicState);
		System.out.println(extrinsicState);
	}

}

享元工厂

package xyz.jangle.design.flyweight;

import java.util.HashMap;
import java.util.Map;

public class FlyweightFactory {
	
	private Map<String, Flyweight> hashMap = new HashMap<String, Flyweight>();
	
	private static FlyweightFactory factory = new FlyweightFactory();
	
	private FlyweightFactory() {}
	/**
	 * 获取唯一实例
	 * @return
	 */
	public static FlyweightFactory getInstance() {
		return factory;
	}
	
	public Flyweight getFlyweight(String key) {
		if(hashMap.containsKey(key)) {
			return hashMap.get(key);
		}else {
			ConcreteFlyweight flyweight = new ConcreteFlyweight(Integer.valueOf(key));
			hashMap.put(key, flyweight);
			return flyweight;
		}
		
	}
	
	

}

客户端（使用）

package xyz.jangle.design.flyweight;

public class AppMain23 {

	public static void main(String[] args) {
		
		FlyweightFactory factory = FlyweightFactory.getInstance();
		
		Flyweight flyweight = factory.getFlyweight("1");
		Flyweight flyweight2 = factory.getFlyweight("2");
		Flyweight flyweight3 = factory.getFlyweight("1");
		System.out.println(flyweight==flyweight2);	//flyweight和flyweight2使用不同的实例，返回false
		System.out.println(flyweight==flyweight3);	//flyweight和flyweight3使用相同的实例，返回true
		
		flyweight.operation(123);

	}

}

输出结果

false
true
1
123