diff --git a/src/main/java/com/github/hcsp/polymorphism/Discount95Strategy.java b/src/main/java/com/github/hcsp/polymorphism/Discount95Strategy.java
index b6ae546..89fc1c6 100644
--- a/src/main/java/com/github/hcsp/polymorphism/Discount95Strategy.java
+++ b/src/main/java/com/github/hcsp/polymorphism/Discount95Strategy.java
@@ -1,3 +1,8 @@
 package com.github.hcsp.polymorphism;
 
-public class Discount95Strategy {}
+public class Discount95Strategy extends PriceCalculator {
+    @Override
+    public int discount(int price,User user){
+        return (int) (price*0.95);
+    }
+}
diff --git a/src/main/java/com/github/hcsp/polymorphism/DiscountStrategy.java b/src/main/java/com/github/hcsp/polymorphism/DiscountStrategy.java
index 66fbd92..f7c5bb6 100644
--- a/src/main/java/com/github/hcsp/polymorphism/DiscountStrategy.java
+++ b/src/main/java/com/github/hcsp/polymorphism/DiscountStrategy.java
@@ -1,6 +1,6 @@
 package com.github.hcsp.polymorphism;
 
-public class DiscountStrategy {
+public class DiscountStrategy extends PriceCalculator {
     public int discount(int price, User user) {
         throw new UnsupportedOperationException();
     }
diff --git a/src/main/java/com/github/hcsp/polymorphism/NoDiscountStrategy.java b/src/main/java/com/github/hcsp/polymorphism/NoDiscountStrategy.java
index bf4c18b..d3a0a61 100644
--- a/src/main/java/com/github/hcsp/polymorphism/NoDiscountStrategy.java
+++ b/src/main/java/com/github/hcsp/polymorphism/NoDiscountStrategy.java
@@ -1,3 +1,9 @@
 package com.github.hcsp.polymorphism;
 
-public class NoDiscountStrategy {}
+public class NoDiscountStrategy extends PriceCalculator {
+    @Override
+    public int discount(int price, User user) {
+        return price;
+    }
+
+}
diff --git a/src/main/java/com/github/hcsp/polymorphism/OnlyVipDiscountStrategy.java b/src/main/java/com/github/hcsp/polymorphism/OnlyVipDiscountStrategy.java
index 1714b1e..e1c2a7c 100644
--- a/src/main/java/com/github/hcsp/polymorphism/OnlyVipDiscountStrategy.java
+++ b/src/main/java/com/github/hcsp/polymorphism/OnlyVipDiscountStrategy.java
@@ -1,3 +1,13 @@
 package com.github.hcsp.polymorphism;
 
-public class OnlyVipDiscountStrategy {}
+public class OnlyVipDiscountStrategy extends PriceCalculator {
+    @Override
+    public int discount(int price,User user){
+        if(user.isVip()){
+            return (int) (price*0.95);
+        }else{
+            return price;
+        }
+    }
+
+}
diff --git a/src/main/java/com/github/hcsp/polymorphism/PriceCalculator.java b/src/main/java/com/github/hcsp/polymorphism/PriceCalculator.java
index 595fe5d..0f5139a 100644
--- a/src/main/java/com/github/hcsp/polymorphism/PriceCalculator.java
+++ b/src/main/java/com/github/hcsp/polymorphism/PriceCalculator.java
@@ -1,28 +1,15 @@
 package com.github.hcsp.polymorphism;
 
-public class PriceCalculator {
+public abstract class PriceCalculator {
     // 使用策略模式重构这个方法，实现三个策略：
     // NoDiscountStrategy 不打折
     // Discount95Strategy 全场95折
     // 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(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!");
-        }
+    public  int calculatePrice(DiscountStrategy strategy, int price, User user) {
+        return strategy.discount(price,user);
+
     }
+
 }