Step2 - 문자열 덧셈 계산기

build.gradle

@@ -14,6 +14,7 @@ dependencies {
     testImplementation 'org.junit.jupiter:junit-jupiter-api:5.14.0'
     testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.14.0'
     testImplementation 'org.junit.platform:junit-platform-launcher:1.14.0'
+    implementation 'org.apache.commons:commons-lang3:3.17.0'
 }
 
 java {

src/main/java/study/StringAddCalculator.java

@@ -0,0 +1,49 @@
+package study;
+
+import org.apache.commons.lang3.StringUtils;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class StringAddCalculator {
+    public static int splitAndSum(String text) {
+        if(StringUtils.isBlank(text)) {
+            return 0;
+        }
+
+        if(text.contains(",") || text.contains(":")) {
+            int sum          = 0;
+            String[] numbers = text.split("[,:]");
+
+            for(String number : numbers) {
+                if(Integer.parseInt(number) < 0) {
+                    throw new RuntimeException(" RuntimeException 예외 발생");
+                }
+
+                sum += Integer.parseInt(number);
+            }
+
+            return sum;
+        }
+
+        if(text.contains("//") || text.contains("\n")) {
+            int sum = 0;
+            Matcher m = Pattern.compile("//(.)\n(.*)").matcher(text);
+            if(m.find()) {
+
+                String customDelimiter = m.group(1);
+                String[] tokens = m.group(2).split(customDelimiter);
+
+                for(String token : tokens) {
+                    sum += Integer.parseInt(token);
+                }
+
+                return sum;
+            }
+        }
+
+
+
+        return Integer.parseInt(text);
+    }
+}

src/test/java/study/StringAddCalculatorTest.java

@@ -0,0 +1,47 @@
+package study;
+
+import org.junit.jupiter.api.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.AssertionsForClassTypes.assertThatThrownBy;
+
+public class StringAddCalculatorTest {
+    @Test
+    public void 문자열_덧셈_null_또는_빈문자열() {
+        int result = StringAddCalculator.splitAndSum(null);
+        assertThat(result).isEqualTo(0);
+
+        result = StringAddCalculator.splitAndSum("");
+        assertThat(result).isEqualTo(0);
+    }
+
+    @Test
+    void 문자열_덧셈_숫자하나() {
+        int result = StringAddCalculator.splitAndSum("2");
+        assertThat(result).isEqualTo(2);
+    }
+
+    @Test
+    void 문자열_덧셈_구분자_덧셈() {
+        int result = StringAddCalculator.splitAndSum("1,2");
+        assertThat(result).isEqualTo(3);
+    }
+
+    @Test
+    void 문자열_덧셈_여러구분자_덧셈() {
+        int result = StringAddCalculator.splitAndSum("1,2:3");
+        assertThat(result).isEqualTo(6);
+    }
+
+    @Test
+    void 문자열_덧셈_커스텀구분자_덧셈() {
+        int result = StringAddCalculator.splitAndSum("//;\n1;2;3");
+        assertThat(result).isEqualTo(6);
+    }
+
+    @Test
+    void 문자열_덧셈_음수예외() {
+        assertThatThrownBy(() -> StringAddCalculator.splitAndSum("-1,2,3"))
+                .isInstanceOf(RuntimeException.class);
+    }
+
+}