设计模式-享元模式

• 抽象享元
• • 食物
• 具体享元
• • 面条
  • 饺子
  • 米饭
• 享元工厂
• • 食堂
• 测试

它尝试重用现有的对象，若没有现成的，则创建对象
主要为了减少创建对象的数量，以减少内存占用，
常用在需要缓冲的场景，例如Java的常量池。

包含抽象享元、具体享元类、享元工厂三个角色。

package com.example.duohoob.dp.flyweight;


public interface Food {

	
	void taste(String extrinsicState);
	
}

package com.example.duohoob.dp.flyweight;


public class Noodle implements Food {

	
	private String intrinsicState = "面条";
	
	@Override
	public void taste(String extrinsicState) {
		// TODO Auto-generated method stub
		System.out.println(extrinsicState + "吃到了" + intrinsicState + "的味道");
	}

}

package com.example.duohoob.dp.flyweight;


public class Dumpling implements Food {

	
	private String intrinsicState = "饺子";
	
	@Override
	public void taste(String extrinsicState) {
		// TODO Auto-generated method stub
		System.out.println(extrinsicState + "吃到了" + intrinsicState + "的味道");
	}

}

package com.example.duohoob.dp.flyweight;


public class Rice implements Food {

	
	private String intrinsicState = "米饭";
	
	@Override
	public void taste(String extrinsicState) {
		// TODO Auto-generated method stub
		System.out.println(extrinsicState + "吃到了" + intrinsicState + "的味道");
	}

}

package com.example.duohoob.dp.flyweight;

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


public class Canteen {

	
	public Map meals = new HashMap();
	
	public Food getFood(String foodName) {
		// 如果没有就现做，相反有的话就不用
		if (!meals.containsKey(foodName)) {
			if ("面条".equals(foodName)) {
				meals.put(foodName, new Noodle());
			}
			if ("饺子".equals(foodName)) {
				meals.put(foodName, new Dumpling());
			}
			if ("米饭".equals(foodName)) {
				meals.put(foodName, new Rice());
			}
		}
		return meals.get(foodName);
	}
	
}

package com.example.duohoob.dp.flyweight;


public class FlyweightTest {

	public static void main(String[] args) {
		Canteen canteen = new Canteen();
		// a要吃面条
		Food noodle1 = canteen.getFood("面条");
		noodle1.taste("a");
		// b要吃面条
		Food noodle2 = canteen.getFood("面条");
		noodle2.taste("b");
		// c要吃饺子
		Food dumpling = canteen.getFood("饺子");
		dumpling.taste("c");
		// d要吃米饭
		Food rice = canteen.getFood("米饭");
		rice.taste("d");
		
		System.out.println();
		System.out.println("abcd共吃了四份饭菜");
		System.out.println("但食堂却只需要准备" + canteen.meals.keySet().size() + "种饭菜");
	}
	
}

运行