Revert "Add1 (#140)"

This reverts commit c1d573f.

src/main/java/com/github/hcsp/polymorphism/Discount95Strategy.java

@@ -1,8 +1,3 @@
 package com.github.hcsp.polymorphism;
 
-public class Discount95Strategy extends DiscountStrategy{
-    @Override
-    public int discount(int price, User user) {
-        return (int)(price * 0.95);
-    }
-}
+public class Discount95Strategy {}

src/main/java/com/github/hcsp/polymorphism/NoDiscountStrategy.java

@@ -1,8 +1,3 @@
 package com.github.hcsp.polymorphism;
 
-public class NoDiscountStrategy extends DiscountStrategy{
-    @Override
-    public int discount(int price, User user) {
-        return price;
-    }
-}
+public class NoDiscountStrategy {}

src/main/java/com/github/hcsp/polymorphism/OnlyVipDiscountStrategy.java

@@ -1,8 +1,3 @@
 package com.github.hcsp.polymorphism;
 
-public class OnlyVipDiscountStrategy extends DiscountStrategy{
-    @Override
-    public int discount(int price, User user) {
-        return user.isVip() ? (int) (price * 0.95) : price;
-    }
-}
+public class OnlyVipDiscountStrategy {}

src/main/java/com/github/hcsp/polymorphism/PriceCalculator.java

@@ -7,8 +7,22 @@ public class PriceCalculator {
     // OnlyVipDiscountStrategy 只有VIP打95折，其他人保持原价
     // 重构后的方法签名：
     // public static int calculatePrice(DiscountStrategy strategy, int price, User user)
-    public static int calculatePrice(DiscountStrategy strategy, int price, User user) {
-        return strategy.discount(price, user);
+    public static int calculatePrice(String discountStrategy, int price, User user) {
+        switch (discountStrategy) {
+            case "NoDiscount":
+                return price;
+            case "Discount95":
+                return (int) (price * 0.95);
+            case "OnlyVip":
+                {
+                    if (user.isVip()) {
+                        return (int) (price * 0.95);
+                    } else {
+                        return price;
+                    }
+                }
+            default:
+                throw new IllegalStateException("Should not be here!");
+        }
     }
-
-}
+}