关于设计模式:设计模式策略模式

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定义：定义了算法家族，别离封装起来，让他们之间能够相互转换，此模式让算法的变动不会影响到应用算法的用户
if…else
类型: 行为型

零碎有很多类，而他们的区别仅仅在于他们的行为不同
一个零碎须要动静地在几种算法中抉择一种

开闭准则
防止应用多种条件转移语句
进步算法的保密性和安全性

客户端必须晓得所有的策略类，并自行决定应用哪一个策略类
产生很多策略类

策略模式和工厂模式
策略模式和状态模式

策略模式加工厂模式

创立策略接口 Promotion

public interface PromotionStrategy {void doPromotion();
}

创立一系列促销策略

public class FanXianPromotionStrategy implements PromotionStrategy{
    @Override
    public void doPromotion() {System.out.println("返现促销, 返回的余额寄存到用户余额中！");
    }
}

public class LiJianPromotionStrategy implements PromotionStrategy {
    @Override
    public void doPromotion() {System.out.println("立减促销, 课程的价格间接减去配置的价格");
    }
}

public class ManJianPromotionStrategy implements PromotionStrategy{
    @Override
    public void doPromotion() {System.out.println("满减促销：满 200 减 20");
    }
}

创立促销流动：用来执行促销策略的类

public class PromotionActivity {
  
    private PromotionStrategy strategy;
  
    public PromotionActivity(PromotionStrategy strategy){this.strategy = strategy;}

    public void executeStrategy(){strategy.doPromotion();
    }
}

创立促销策略工厂

/**
 * @program: design_pattern
 * @description: 促销策略工厂
 * @create: 2021-10-13 22:23
 **/
public class PromotionStrategyFactory {

    /** 私有化结构器  */
    private PromotionStrategyFactory(){}

    private static  final Map<String,PromotionStrategy>  PROMOTION_STRATEGY_MAP = new HashMap<>();

    // 初始化工厂
    static {PROMOTION_STRATEGY_MAP.put(PromotionType.FANXIAN,new FanXianPromotionStrategy());
        PROMOTION_STRATEGY_MAP.put(PromotionType.LIJIAN,new LiJianPromotionStrategy());
        PROMOTION_STRATEGY_MAP.put(PromotionType.MANJIAN,new ManJianPromotionStrategy());
    }

    /** 对外提供获取策略的办法 */
    public  static PromotionStrategy getPromotionStrategy(String promotionKey){PromotionStrategy promotionStrategy = PROMOTION_STRATEGY_MAP.get(promotionKey);
        return promotionStrategy == null?null:promotionStrategy;
    }

    private interface PromotionType{
         String LIJIAN = "LIJIAN";
         String MANJIAN = "MANJIAN";
         String FANXIAN = "FANXIAN";
    }

}

测试类

public class Test {public static void main(String[] args) {
        String promotionKey = "LIJIAN";
        PromotionActivity promotionActivity = 
          new PromotionActivity(PromotionStrategyFactory.getPromotionStrategy(promotionKey));
        promotionActivity.executeStrategy();}
}