Strategy Pattern

oop-in-spring/practice/design-pattern/strategyPattern/after/Calculator.java

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+package strategyPattern.after;
+
+import java.util.List;
+
+public class Calculator {
+
+    private DiscountStrategy discountStrategy;
+
+    public Calculator(DiscountStrategy discountStrategy){
+        this.discountStrategy = discountStrategy;
+    }
+
+    public int calculate(List<Item> items){
+        int sum = 0;
+        for (Item item : items){
+            sum += discountStrategy.getDiscountPrice(item);
+        }
+        return sum;
+    }
+}

oop-in-spring/practice/design-pattern/strategyPattern/after/DiscountStrategy.java

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+package strategyPattern.after;
+
+public interface DiscountStrategy {
+    int getDiscountPrice(Item item);
+}

oop-in-spring/practice/design-pattern/strategyPattern/after/FirstGuestDiscountStrategy.java

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+package strategyPattern.after;
+
+public class FirstGuestDiscountStrategy implements DiscountStrategy{
+
+    @Override
+    public int getDiscountPrice(Item item) {
+        return (int) (item.getPrice() * 0.9);
+    }
+}

oop-in-spring/practice/design-pattern/strategyPattern/after/Item.java

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+package strategyPattern.after;
+
+public class Item {
+    private int price;
+
+    public int getPrice() {
+        return price;
+    }
+
+    public void setPrice(int price) {
+        this.price = price;
+    }
+}

oop-in-spring/practice/design-pattern/strategyPattern/after/LastGuestDiscountStrategy.java

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+package strategyPattern.after;
+
+public class LastGuestDiscountStrategy implements DiscountStrategy {
+    @Override
+    public int getDiscountPrice(Item item) {
+        return (int) (item.getPrice() * 0.5);
+    }
+}

oop-in-spring/practice/design-pattern/strategyPattern/after/StrategyMain.java

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+package strategyPattern.after;
+
+import java.util.List;
+
+public class StrategyMain {
+
+    private DiscountStrategy strategy;
+    private List<Item> items;
+
+    public static void main(String[] args) {
+
+    }
+
+    public void onFirstGuestButtonClick(){
+        // 첫 손님 할인 버튼 누를 때 객체 생성
+        strategy = new FirstGuestDiscountStrategy();
+    }
+
+    public void onLastGuestButtonClick(){
+        // 마지막 손님 대폭 할인 버튼 누를 때 객체 생성
+        strategy = new LastGuestDiscountStrategy();
+    }
+
+    public void onCalculationButtonClick(){
+        // 계산 버튼 누를 때 실행
+        Calculator cal = new Calculator(strategy);
+        int price = cal.calculate(items);
+
+    }
+}

oop-in-spring/practice/design-pattern/strategyPattern/before/Calculator.java

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+package strategyPattern.before;
+
+public class Calculator {
+    public int calculate(boolean firstGuest, List<item> items){
+        int sum = 0;
+        for (Item item : items){
+            if(firstGuest) {
+                sum += (int)(item.getPrice()*0.9);
+            } else if(!item.isFresh()) {
+                sum += (int)(item.getPrice()*0.8);
+            } else {
+                sum += item.getPrice();
+            }
+        }
+        return sum;
+    }
+}