refactoring : long parameter list - replace parameter with query

refactoring/src/main/java/com/example/refactoring/_04_long_parameter_list/_00_before/Order.java

@@ -0,0 +1,23 @@
+package com.example.refactoring._04_long_parameter_list._00_before;
+
+public class Order {
+
+    private int quantity;
+
+    private double itemPrice;
+
+    public Order(int quantity, double itemPrice) {
+        this.quantity = quantity;
+        this.itemPrice = itemPrice;
+    }
+
+    public double finalPrice() {
+        double basePrice = this.quantity * this.itemPrice;
+        int discountLevel = this.quantity > 100 ? 2 : 1;
+        return this.discountedPrice(basePrice, discountLevel);
+    }
+
+    private double discountedPrice(double basePrice, int discountLevel) {
+        return discountLevel == 2 ? basePrice * 0.9 : basePrice * 0.95;
+    }
+}

refactoring/src/main/java/com/example/refactoring/_04_long_parameter_list/_14_replace_parameter_with_query/Order.java

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+package com.example.refactoring._04_long_parameter_list._14_replace_parameter_with_query;
+
+public class Order {
+
+    private int quantity;
+
+    private double itemPrice;
+
+    public Order(int quantity, double itemPrice) {
+        this.quantity = quantity;
+        this.itemPrice = itemPrice;
+    }
+
+    public double finalPrice() {
+        double basePrice = this.quantity * this.itemPrice;
+
+        // 함수를 호출하는 쪽의 책임을 줄인다.
+        return this.discountedPrice(basePrice);
+    }
+
+    private int getDiscountLevel() {
+        return this.quantity > 100 ? 2 : 1;
+    }
+
+    private double discountedPrice(double basePrice) {
+        return getDiscountLevel() == 2 ? basePrice * 0.9 : basePrice * 0.95;
+    }
+}

refactoring/src/test/java/com/example/refactoring/_04_long_parameter_list/_00_before/OrderTest.java

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+package com.example.refactoring._04_long_parameter_list._00_before;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class OrderTest {
+
+    @Test
+    void discountedPriceWithDiscountLevel2() {
+        int quantity = 200;
+        double price = 100;
+        assertEquals(quantity * price * 0.90, new Order(quantity, price).finalPrice());
+    }
+
+    @Test
+    void discountedPriceWithDiscountLevel1() {
+        int quantity = 100;
+        double price = 100;
+        assertEquals(quantity * price * 0.95, new Order(quantity, price).finalPrice());
+    }
+}

refactoring/src/test/java/com/example/refactoring/_04_long_parameter_list/_14_replace_parameter_with_query/OrderTest.java

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+package com.example.refactoring._04_long_parameter_list._14_replace_parameter_with_query;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class OrderTest {
+
+    @Test
+    void discountedPriceWithDiscountLevel2() {
+        int quantity = 200;
+        double price = 100;
+        assertEquals(quantity * price * 0.90, new Order(quantity, price).finalPrice());
+    }
+
+    @Test
+    void discountedPriceWithDiscountLevel1() {
+        int quantity = 100;
+        double price = 100;
+        assertEquals(quantity * price * 0.95, new Order(quantity, price).finalPrice());
+    }
+}