2단계 - 문자열 계산기

src/main/java/StringAddCalculator.java

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+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class StringAddCalculator {
+
+    public static final String COMMA = ",";
+    public static final String DELIMETER = ",|:";
+    public static final String CUSTOMDELIMETER = "//(.)\n(.*)";
+    public static final int DEFAULT_VALUE_OF_NULL_AND_EMPTYSTRING = 0;
+    public static final Pattern pattern = Pattern.compile(CUSTOMDELIMETER);
+
+    private StringAddCalculator() {
+        throw new RuntimeException();
+    }
+
+    public static int splitAndSum(String input) {
+        if (input == null || input.isEmpty()) {
+            return DEFAULT_VALUE_OF_NULL_AND_EMPTYSTRING;
+        }
+        Matcher m = pattern.matcher(input);
+        if (m.find()) {
+            String customDelimiter = m.group(1);
+            String[] tokens = m.group(2).split(customDelimiter);
+            return calculateSum(toInt(tokens));
+        }
+        String[] splited = input.split(DELIMETER);
+        return calculateSum(toInt(splited));
+    }
+
+    private static int calculateSum(int[] splited) {
+        int summation = 0;
+        for (int num : splited) {
+            isNegative(num);
+            summation += num;
+        }
+        return summation;
+    }
+
+    private static void isNegative(int num) {
+        if (num < 0) {
+            throw new RuntimeException();
+        }
+    }
+
+    private static int[] toInt(String[] splited) {
+        int[] numbers = new int[splited.length];
+        for (int i = 0; i < splited.length; i++) {
+            numbers[i] = Integer.parseInt(checkDigit(splited[i]));
+        }
+        return numbers;
+    }
+
+    private static String checkDigit(String input) {
+        for (char c : input.toCharArray()) {
+            valudateDigit(c);
+        }
+        return input;
+    }
+
+    private static void valudateDigit(char c) {
+        if (!Character.isDigit(c)) {
+            throw new RuntimeException();
+        }
+    }
+}

src/test/java/SetCollectionTest.java

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+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class SetCollectionTest {
+    private Set<Integer> numbers;
+
+    @BeforeEach
+    void setUp() {
+        numbers = new HashSet<>();
+        numbers.add(1);
+        numbers.add(1);
+        numbers.add(2);
+        numbers.add(3);
+    }
+
+    @Test
+    @DisplayName("size()로 Set의 크기 확인")
+    void sizeTest() {
+        assertThat(numbers).hasSize(3);
+    }
+
+
+    @ParameterizedTest
+    @ValueSource(ints = {1, 2, 3})
+    @DisplayName("contains()로 set에 있는 값 확인")
+    void containsTest(int number) {
+        assertThat(numbers.contains(number));
+    }
+
+    @ParameterizedTest
+    @CsvSource(value = {"1:true", "2:true", "3:true", "4:false", "5:false"}, delimiter = ':')
+    @DisplayName("contains()로 다양한 값 확인")
+    void containsTest2(int value, boolean expected) {
+        assertThat(numbers.contains(value)).isEqualTo(expected);
+    }
+}

src/test/java/StringAddCalculatorTest.java

@@ -0,0 +1,64 @@
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.EmptySource;
+import org.junit.jupiter.params.provider.NullSource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+class StringAddCalculatorTest {
+    @ParameterizedTest
+    @EmptySource
+    @NullSource
+    @DisplayName("빈 문자열 또는 null이면 0을 반환")
+    void whenGivenNullOrEmpty(String input) {
+        int result = StringAddCalculator.splitAndSum(input);
+
+        assertThat(result).isEqualTo(0);
+    }
+
+    @Test
+    @DisplayName("숫자 하나를 입력할 경우 해당 숫자를 반환한다")
+    void inputOneNumberStringReturnToInteger() {
+        int result = StringAddCalculator.splitAndSum("1");
+
+        assertThat(result).isEqualTo(1);
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"1,2"})
+    @DisplayName("숫자 두개를 컴마(,) 구분자로 입력할 경우 두 숫자의 합을 반환")
+    void splitAndSumWithComma(String input) {
+        int result = StringAddCalculator.splitAndSum(input);
+
+        assertThat(result).isEqualTo(3);
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"1,2:3"})
+    @DisplayName("구분자를 컴마 이외에 콜론을 사용할 수 있다")
+    void splitAndSumWithCommaOrColon(String input) {
+        int result = StringAddCalculator.splitAndSum(input);
+
+        assertThat(result).isEqualTo(6);
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"//;\n1;2;3"})
+    @DisplayName("\"//\"와 \"\\n\" 사이의 문자를 커스텀 구분자 사용")
+    void customDelimeter(String input) {
+        int result = StringAddCalculator.splitAndSum(input);
+
+        assertThat(result).isEqualTo(6);
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"-1,2,3"})
+    @DisplayName("음수를 전달할 경우 RuntimeException 발생")
+    void negativeThrowRuntimeException(String input) {
+        assertThatThrownBy(() -> StringAddCalculator.splitAndSum(input))
+                .isInstanceOf(RuntimeException.class);
+    }
+}

src/test/java/StringClassTest.java

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+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+class StringClassTest {
+    @Test
+    @DisplayName("\"1,2\"를 ,로 split 했을 때 분리되는지")
+    void splitTest1() {
+        //given
+        String str = "1,2";
+
+        //when
+        String[] result = str.split(",");
+
+        //Then
+        assertThat(result).containsExactly("1", "2");
+    }
+
+    @Test
+    @DisplayName("\"1\"을 ,로 split 했을 때 {\"1\"}로 반환되는지")
+    void splitTest2() {
+        String[] result = "1".split(",");
+
+        assertThat(result).contains("1");
+    }
+
+    @Test
+    @DisplayName("substring()을 통해 ()제거")
+    void subStringTest() {
+        String str = "(1,2)";
+
+        String result = str.substring(1, str.length() - 1);
+
+        assertThat(result).isEqualTo("1,2");
+    }
+
+    @Test
+    @DisplayName("charAt()을 통해 문자열 범위 안 문자 가져오기")
+    void charAt_범위_안() {
+        final String str = "abc";
+
+        char result = str.charAt(1);
+
+        assertThat(result).isEqualTo('b');
+    }
+
+    @Test
+    @DisplayName("charAt()을 통해 문자열 범위 밖 문자 가져오기")
+    void charAt_범위_밖() {
+        final String str = "abc";
+
+        assertThatThrownBy(() -> {
+            str.charAt(str.length());
+        }).isInstanceOf(IndexOutOfBoundsException.class)
+                .hasMessageContaining("String index out of range:");
+    }
+
+}