2단계 - 문자열 덧셈 계산기

src/main/java/step2/NumberSeparator.java

@@ -0,0 +1,54 @@
+package step2;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import utils.StringUtils;
+
+public class NumberSeparator {
+
+    private static final String DEFAULT_DELIMITER = "[,:]";
+    private static final String DELIMITER_FIND_REGEX = "//(.)\n(.*)";
+
+    public List<Integer> separate(String input) {
+        if (StringUtils.isEmpty(input)) {
+            return List.of(0);
+        }
+        if (StringUtils.isNumeric(input)) {
+            return List.of(Integer.parseInt(input));
+        }
+        Pattern pattern = Pattern.compile(DELIMITER_FIND_REGEX);
+        Matcher matcher = pattern.matcher(input);
+
+        String[] values;
+        if (matcher.find()) {
+            String customDelimiter = matcher.group(1);
+            values = matcher.group(2).split(customDelimiter);
+        } else {
+            values = input.split(DEFAULT_DELIMITER);
+        }
+        return convertStringArrayToIntegerList(values);
+    }
+
+    private List<Integer> convertStringArrayToIntegerList(String[] values) {
+        List<Integer> members = new ArrayList<>();
+        for (String value : values) {
+            members.add(parseAndCheck(value));
+        }
+        return members;
+    }
+
+    private Integer parseAndCheck(String input) {
+        int value;
+        try {
+            value = Integer.parseInt(input);
+        } catch (NumberFormatException e) {
+            throw new RuntimeException("숫자가 아닌 값이 입력되었습니다.");
+        }
+        if (value < 0) {
+            throw new RuntimeException("음수는 입력할 수 없습니다.");
+        }
+        return value;
+    }
+}

src/main/java/step2/StringAddCalculator.java

@@ -0,0 +1,21 @@
+package step2;
+
+
+import java.util.List;
+
+public class StringAddCalculator {
+
+    private final static NumberSeparator numberSeparator = new NumberSeparator();
+
+
+    public static int splitAndSum(String o) {
+        List<Integer> splitNumber = numberSeparator.separate(o);
+        return sum(splitNumber);
+    }
+
+    private static int sum(List<Integer> splitNumber) {
+        return splitNumber.stream()
+            .mapToInt(Integer::intValue)
+            .sum();
+    }
+}

src/main/java/utils/StringUtils.java

@@ -0,0 +1,18 @@
+package utils;
+
+public class StringUtils {
+
+    public StringUtils() {
+    }
+
+    public static boolean isEmpty(String str) {
+        return str == null || str.isEmpty();
+    }
+
+    public static boolean isNumeric(String str) {
+        if (isEmpty(str)) {
+            return false;
+        }
+        return str.matches("\\d+");
+    }
+}

src/test/java/step2/StringAddCalculatorTest.java

@@ -0,0 +1,54 @@
+package step2;
+
+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);
+    }
+
+    @Test
+    public void splitAndSum_문자포함() throws Exception {
+        assertThatThrownBy(() -> StringAddCalculator.splitAndSum("1,2,test"))
+            .isInstanceOf(RuntimeException.class);
+    }
+}

src/test/java/study/StringTest.java

@@ -9,20 +9,20 @@
 public class StringTest {
 
     @Test
-    void Split() {
+    void split() {
         String[] splitText = "1,2".split(",");
         assertThat(splitText).containsExactly("1", "2");
     }
 
     @Test
-    void Substring() {
+    void substring() {
         String text = "(1,2)";
         String substringText = text.substring(1, text.length() - 1);
         assertThat(substringText).isEqualTo("1,2");
     }
 
     @Test
-    void CharAt() {
+    void charAt() {
         String text = "abc";
         assertThat(text.charAt(0)).isEqualTo('a');
         assertThat(text.charAt(1)).isEqualTo('b');