设计模式-18-享元

简介：使用共享物件，用来尽可能减少内存使用量以及分享资讯给尽可能多的相似物件

目的：

总结：通过共享模式减少内存使用和重复对象

组成：享元管理器， 享元， 辅助类
1，享元

package com.design.r.flyweight;
/**
 * 英雄基类
 */
public abstract class Hero {
    
    
    protected String userName;               //英雄名称
    protected String[] kills = new String[4];//技能
    
    public Hero() {
        super();
        this.userName = getUserName();
        initKills();
    }

    public void attact(){
        System.out.println(userName + " 发动了物理攻击!");
    }
    
    public abstract String getUserName();
    public abstract void initKills();
    
}

package com.design.r.flyweight;
/**
 * 英雄A
 */
public class HeroA extends Hero {

    @Override
    public String getUserName() {
        return "英雄A";
    }

    @Override
    public void initKills() {
        kills[0] = "技能A-1";
        kills[1] = "技能A-2";
        kills[2] = "技能A-3";
        kills[3] = "技能A-4";
    }

}

package com.design.r.flyweight;
/**
 * 英雄B
 */
public class HeroB extends Hero {

    @Override
    public String getUserName() {
        return "英雄B";
    }

    @Override
    public void initKills() {
        kills[0] = "技能B-1";
        kills[1] = "技能B-2";
        kills[2] = "技能B-3";
        kills[3] = "技能B-4";
    }

}

2，辅助类

package com.design.r.flyweight;
/**
 * 英雄状态和技能的组合
 */
public class Role {
    
    private Hero hero;//英雄
    private Long bp; //血量
    private Long mp; //蓝量
    
    public Role(Hero hero) {
        super();
        this.hero = hero;
    }
    
    public void attact(){
        hero.attact();
    }

    public Long getBp() {
        return bp;
    }

    public void setBp(Long bp) {
        this.bp = bp;
    }

    public Long getMp() {
        return mp;
    }

    public void setMp(Long mp) {
        this.mp = mp;
    }

}

3，享元管理器

package com.design.r.flyweight;

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

/**
 * 对英雄单例管理, 达到共享功能
 */
public class HeroManager {
    
    private static HeroManager heroManager  = new HeroManager();
    private Map<String, Hero> heroMap = new HashMap<>();
    
    public static HeroManager getInstance(){
        return heroManager;
    }
    
    public Hero getHero(String userName){
        Hero hero = heroMap.get(userName);
        if(hero == null){
            if("英雄A".equals(userName)){
                hero = new HeroA();
            }else if("英雄B".equals(userName)){
                hero = new HeroB();
            }
            heroMap.put(userName, hero);
            return hero;
        }else{
            return hero;
        }
    }

}

4，Main

package com.design.r.flyweight;
/**
 * 18-享元模式
 * 
 * 通过共享模式减少内存使用和重复对象
 */
public class MainTest {

    public static void main(String[] args) {
        
        //使用享元模式后,再创建了4个英雄后,HeroA和HeroB都是单例并没有产生4个实例
        
        HeroManager heroManager = new HeroManager();
        Role hero1 = new Role(heroManager.getHero("英雄A"));
        Role hero2 = new Role(heroManager.getHero("英雄A"));
        
        Role hero3 = new Role(heroManager.getHero("英雄B"));
        Role hero4 = new Role(heroManager.getHero("英雄B"));
    }
}