문자열 덧셈 계산기

src/main/java/StringAddCalculator.java

@@ -0,0 +1,43 @@
+import java.util.Arrays;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class StringAddCalculator {
+    public static boolean isValidationCheckNullOrEmpty(String str) {
+            return str == null || str.isEmpty();
+        }
+
+    public static boolean isValidationCheckSize1(String str) {
+        return str.length() == 1;
+    }
+
+    private static int standardStringAddCalculator(String text) {
+        String[] numbers = text.split(",|:");
+        if(Arrays.toString(numbers).contains("-")){
+            throw new RuntimeException();
+        }
+        return Arrays.stream(numbers).mapToInt(Integer::parseInt).sum();
+    }
+
+    private static Integer customDelimiterAddCalculator(String str) {
+        Matcher m = Pattern.compile("//(.)\n(.*)").matcher(str);
+        if (m.find()) {
+            String customDelimiter = m.group(1);
+            String[] numbers = m.group(2).split(customDelimiter);
+
+            return Arrays.stream(numbers).mapToInt(Integer::parseInt).sum();
+        }
+        return null;
+    }
+
+    public static int splitAndSum(String str) {
+        if(isValidationCheckNullOrEmpty(str)) return 0;
+        if(isValidationCheckSize1(str)) return Integer.parseInt(str);
+
+        try{ return standardStringAddCalculator(str);}
+        catch (NumberFormatException numberFormatException){
+        return customDelimiterAddCalculator(str);
+        }
+
+    }
+}

src/test/java/StringAddCalculatorTest.java

@@ -0,0 +1,45 @@
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+import static org.assertj.core.api.AssertionsForClassTypes.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);
+    }
+}