初级策略模式

src/main/java/top/fjy8018/designpattern/pattern/behavior/strategy/FanXianPromotionStrategy.java

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+package top.fjy8018.designpattern.pattern.behavior.strategy;
+
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * 返现促销策略
+ *
+ * @author F嘉阳
+ * @date 2020/3/4 15:38
+ */
+@Slf4j
+public class FanXianPromotionStrategy implements PromotionStrategy {
+    @Override
+    public void doPromotion() {
+        log.info("返现促销，返回金额存放到用户余额中");
+    }
+}

src/main/java/top/fjy8018/designpattern/pattern/behavior/strategy/LiJianPromotionStrategy.java

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+package top.fjy8018.designpattern.pattern.behavior.strategy;
+
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * 立减促销策略
+ *
+ * @author F嘉阳
+ * @date 2020/3/4 15:39
+ */
+@Slf4j
+public class LiJianPromotionStrategy implements PromotionStrategy {
+    @Override
+    public void doPromotion() {
+        log.info("立减促销，课程价格直接减去配置的价格");
+    }
+}

src/main/java/top/fjy8018/designpattern/pattern/behavior/strategy/ManJianPromotionStrategy.java

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+package top.fjy8018.designpattern.pattern.behavior.strategy;
+
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * 满减促销策略
+ *
+ * @author F嘉阳
+ * @date 2020/3/4 15:38
+ */
+@Slf4j
+public class ManJianPromotionStrategy implements PromotionStrategy {
+    @Override
+    public void doPromotion() {
+        log.info("满减促销，满200-20");
+    }
+}

src/main/java/top/fjy8018/designpattern/pattern/behavior/strategy/PromotionActivity.java

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+package top.fjy8018.designpattern.pattern.behavior.strategy;
+
+/**
+ * 促销包装类
+ *
+ * @author F嘉阳
+ * @date 2020/3/4 15:42
+ */
+public class PromotionActivity {
+
+    private PromotionStrategy promotionStrategy;
+
+    public PromotionActivity(PromotionStrategy promotionStrategy) {
+        this.promotionStrategy = promotionStrategy;
+    }
+
+    /**
+     * 执行促销逻辑
+     */
+    public void executePromotionStrategy() {
+        this.promotionStrategy.doPromotion();
+    }
+}

src/main/java/top/fjy8018/designpattern/pattern/behavior/strategy/PromotionStrategy.java

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+package top.fjy8018.designpattern.pattern.behavior.strategy;
+
+/**
+ * 促销接口
+ *
+ * @author F嘉阳
+ * @date 2020/3/4 15:37
+ */
+public interface PromotionStrategy {
+
+    void doPromotion();
+}

src/test/java/top/fjy8018/designpattern/pattern/behavior/strategy/PromotionStrategyTest.java

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+package top.fjy8018.designpattern.pattern.behavior.strategy;
+
+import lombok.extern.slf4j.Slf4j;
+import org.apache.commons.lang3.StringUtils;
+import org.junit.jupiter.api.Test;
+
+/**
+ * @author F嘉阳
+ * @date 2020/3/4 15:46
+ */
+@Slf4j
+class PromotionStrategyTest {
+
+    @Test
+    void existIfElse() {
+        String promotionKey = "LIJIAN";
+        PromotionActivity activity = null;
+        if (StringUtils.equals(promotionKey, "LIJIAN")) {
+            // 方法和类本身线程安全
+            activity = new PromotionActivity(new LiJianPromotionStrategy());
+        } else if (StringUtils.equals(promotionKey, "MANJIAN")) {
+            activity = new PromotionActivity(new FanXianPromotionStrategy());
+        }
+
+        activity.executePromotionStrategy();
+    }
+}