add interface

src/main/java/core/basesyntax/DiscountStrategy.java

@@ -0,0 +1,27 @@
+package core.basesyntax;
+
+import core.basesyntax.strategy.DiscountService;
+import core.basesyntax.strategy.impl.BirthdayDiscountService;
+import core.basesyntax.strategy.impl.BlackFridayDiscountService;
+import core.basesyntax.strategy.impl.DefaultDiscountService;
+import core.basesyntax.strategy.impl.NewYearDiscountService;
+
+public class DiscountStrategy {
+
+    public DiscountService getDiscountServiceBySpecialEvent(String specialEvent) {
+        if (specialEvent == null) {
+            return new DefaultDiscountService();
+        }
+
+        switch (specialEvent.toLowerCase()) {
+            case "birthday":
+                return new BirthdayDiscountService();
+            case "black friday":
+                return new BlackFridayDiscountService();
+            case "new year":
+                return new NewYearDiscountService();
+            default:
+                return new DefaultDiscountService();
+        }
+    }
+}

src/main/java/core/basesyntax/Main.java

@@ -0,0 +1,13 @@
+package core.basesyntax;
+
+public class Main {
+    public static void main(String[] args) {
+        /*System.out.println("+++");
+
+        DiscountStrategy discountStrategy = new DiscountStrategy();
+        DiscountService discountService = discountStrategy
+                .getDiscountServiceBySpecialEvent("birthday");
+        double discount = discountService.getDiscount();
+        System.out.println(discount);*/
+    }
+}

src/main/java/core/basesyntax/strategy/DiscountService.java

@@ -0,0 +1,6 @@
+package core.basesyntax.strategy;
+
+public interface DiscountService {
+    double getDiscount();
+
+}

src/main/java/core/basesyntax/strategy/impl/BirthdayDiscountService.java

@@ -0,0 +1,10 @@
+package core.basesyntax.strategy.impl;
+
+import core.basesyntax.strategy.DiscountService;
+
+public class BirthdayDiscountService implements DiscountService {
+    @Override
+    public double getDiscount() {
+        return 33;
+    }
+}

src/main/java/core/basesyntax/strategy/impl/BlackFridayDiscountService.java

@@ -0,0 +1,10 @@
+package core.basesyntax.strategy.impl;
+
+import core.basesyntax.strategy.DiscountService;
+
+public class BlackFridayDiscountService implements DiscountService {
+    @Override
+    public double getDiscount() {
+        return 45;
+    }
+}

src/main/java/core/basesyntax/strategy/impl/DefaultDiscountService.java

@@ -0,0 +1,10 @@
+package core.basesyntax.strategy.impl;
+
+import core.basesyntax.strategy.DiscountService;
+
+public class DefaultDiscountService implements DiscountService {
+    @Override
+    public double getDiscount() {
+        return 0;
+    }
+}

src/main/java/core/basesyntax/strategy/impl/NewYearDiscountService.java

@@ -0,0 +1,10 @@
+package core.basesyntax.strategy.impl;
+
+import core.basesyntax.strategy.DiscountService;
+
+public class NewYearDiscountService implements DiscountService {
+    @Override
+    public double getDiscount() {
+        return 20;
+    }
+}

src/test/java/core/basesyntax/StrategyTest.java

@@ -26,7 +26,7 @@ public void getDiscountBySpecialEvent_IsOk() {
       DiscountStrategy discountStrategy = new DiscountStrategy();
       double expectedDiscount = specialEventsDiscounts.get(specialEvent);
       double actualDiscount = discountStrategy.getDiscountServiceBySpecialEvent(specialEvent)
-          .getDiscount();
+              .getDiscount();
       Assert.assertEquals("Expected discount of " + specialEvent + " " + expectedDiscount
               + ",but your discount " + actualDiscount,
           expectedDiscount, actualDiscount, DELTA);