feat: Converter 인터페이스와 StringToIntegerConverter 객체 구현

Author: wonu606

calculator/src/main/java/com/wonu606/calculator/CalculatorApp.java

@@ -1,6 +1,8 @@
 package com.wonu606.calculator;
 
 import com.wonu606.app.App;
+import com.wonu606.calculator.converter.Converter;
+import com.wonu606.calculator.converter.StringToIntegerConverter;
 import com.wonu606.calculator.storage.Persistence;
 import com.wonu606.calculator.storage.ResultStore;
 import com.wonu606.calculator.strategy.Strategy;
@@ -31,8 +33,9 @@ public void execute(Input input, Print printer) throws IOException {
         this.input = input;
         this.printer = printer;
 
+        Converter<String, Integer> stringIntegerConverter = new StringToIntegerConverter();
         while (true) {
-            int selection = Integer.parseInt(input.getInput());
+            int selection = stringIntegerConverter.convert(input.getInput());
 
             Optional<Strategy> selectedStrategy =
                     Optional.ofNullable(strategies.get(selection - 1));

calculator/src/main/java/com/wonu606/calculator/converter/Converter.java

@@ -0,0 +1,6 @@
+package com.wonu606.calculator.converter;
+
+public interface Converter<T, R> {
+
+    R convert(T input);
+}

calculator/src/main/java/com/wonu606/calculator/converter/StringToIntegerConverter.java

@@ -0,0 +1,17 @@
+package com.wonu606.calculator.converter;
+
+import com.wonu606.util.Message;
+
+public class StringToIntegerConverter implements Converter<String, Integer> {
+
+    @Override
+    public Integer convert(String input) {
+        Integer result = null;
+        try {
+            result = Integer.parseInt(input);
+        } catch (NumberFormatException exception) {
+            throw new IllegalArgumentException(Message.INVALID_INPUT);
+        }
+        return result;
+    }
+}

calculator/src/main/java/com/wonu606/util/Message.java

@@ -3,4 +3,5 @@
 public abstract class Message {
     public static final String INVALID_ORDER = "잘못된 순번입니다.";
     public static final String INVALID_NUMBER = "잘못된 번호입니다.";
+    public static final String INVALID_INPUT = "잘못된 입력입니다.";
 }

calculator/src/test/java/com/wonu606/converter/StringIntegerConverterTest.java

@@ -0,0 +1,39 @@
+package com.wonu606.converter;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatCode;
+
+import com.wonu606.calculator.converter.Converter;
+import com.wonu606.calculator.converter.StringToIntegerConverter;
+import com.wonu606.util.Message;
+import org.junit.jupiter.api.Test;
+
+public class StringIntegerConverterTest {
+
+    Converter<String, Integer> converter = new StringToIntegerConverter();
+
+    @Test
+    void testIfNumber() {
+        String input = "123123";
+
+        assertThat(converter.convert(input)).isEqualTo(123123);
+    }
+
+    @Test
+    void testOverflow() {
+        String input = "2147483648";
+
+        assertThatCode(() -> converter.convert(input))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining(Message.INVALID_INPUT);
+    }
+
+    @Test
+    void testIfNotNumber() {
+        String input = "111ㅁ";
+
+        assertThatCode(() -> converter.convert(input))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining(Message.INVALID_INPUT);
+    }
+}