🚀 2단계 - 문자열 덧셈 계산기

src/main/java/StringAddCalculator.java

@@ -0,0 +1,56 @@
+import java.util.Arrays;
+import java.util.Objects;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class StringAddCalculator {
+
+    private static final String DELIMITER = "[,:;]";
+    private static final String DELIMITER_REGEX = "//(.)\n(.*)";
+    private static final Pattern PATTERN = Pattern.compile(DELIMITER_REGEX);
+
+    public static int splitAndSum(String text) {
+        if (Objects.isNull(text) || text.isBlank()) {
+            return 0;
+        }
+        return sum(toInt(split(text)));
+    }
+
+    private static String[] split(String text) {
+        Matcher matcher = PATTERN.matcher(text);
+        if (!matcher.find()) {
+            return text.split(DELIMITER);
+        }
+
+        String customDelimiter = matcher.group(1);
+        String delimitedText = matcher.group(2);
+        return delimitedText.split(customDelimiter);
+    }
+
+    private static int[] toInt(String[] texts) {
+        return Arrays.stream(texts)
+            .mapToInt(StringAddCalculator::toIntOrThrow)
+            .toArray();
+    }
+
+    private static int toIntOrThrow(String text) {
+        try {
+            int parsedValue = toInt(text);
+            if (parsedValue < 0) {
+                throw new NumberFormatException();
+            }
+            return parsedValue;
+        } catch (NumberFormatException e) {
+            throw new RuntimeException();
+        }
+    }
+
+    private static int toInt(String text) {
+        return Integer.parseInt(text);
+    }
+
+    private static int sum(int[] values) {
+        return Arrays.stream(values)
+            .sum();
+    }
+}

src/test/java/SetTest.java

@@ -24,15 +24,13 @@ void setUp() {
 
     @Test
     void 컬렉션_크기_구하기() {
-        int size = this.numbers.size();
-
-        assertThat(size).isEqualTo(3);
+        assertThat(this.numbers).hasSize(3);
     }
 
     @ParameterizedTest
     @ValueSource(ints = {1, 2, 3})
     void 숫자_포함여부_확인(int value) {
-        assertThat(this.numbers.contains(value)).isTrue();
+        assertThat(this.numbers).contains(value);
     }
 
     @ParameterizedTest

src/test/java/StringAddCalculatorTest.java

@@ -0,0 +1,46 @@
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+public class StringAddCalculatorTest {
+
+    @Test
+    public void splitAndSum_null_또는_빈문자() {
+        int result = StringAddCalculator.splitAndSum(null);
+        assertThat(result).isEqualTo(0);
+
+        result = StringAddCalculator.splitAndSum("");
+        assertThat(result).isEqualTo(0);
+    }
+
+    @Test
+    public void splitAndSum_숫자하나() throws Exception {
+        int result = StringAddCalculator.splitAndSum("1");
+        assertThat(result).isEqualTo(1);
+    }
+
+    @Test
+    public void splitAndSum_쉼표구분자() throws Exception {
+        int result = StringAddCalculator.splitAndSum("1,2");
+        assertThat(result).isEqualTo(3);
+    }
+
+    @Test
+    public void splitAndSum_쉼표_또는_콜론_구분자() throws Exception {
+        int result = StringAddCalculator.splitAndSum("1,2:3");
+        assertThat(result).isEqualTo(6);
+    }
+
+    @Test
+    public void splitAndSum_custom_구분자() throws Exception {
+        int result = StringAddCalculator.splitAndSum("//;\n1;2;3");
+        assertThat(result).isEqualTo(6);
+    }
+
+    @Test
+    public void splitAndSum_negative() throws Exception {
+        assertThatThrownBy(() -> StringAddCalculator.splitAndSum("-1,2,3"))
+            .isInstanceOf(RuntimeException.class);
+    }
+}