Implement the StringAddCalculator

src/main/java/StringAddCalculator/controller/StringAddCalculator.java

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+package StringAddCalculator.controller;
+
+import StringAddCalculator.domain.Computation;
+import StringAddCalculator.view.InputView;
+
+
+public class StringAddCalculator {
+    final static private Computation computation = new Computation();
+    public static void main(String[] args){
+        InputView inputView = new InputView();
+        computation.getNumber(inputView.askAddNumber());
+    }
+}

src/main/java/StringAddCalculator/domain/Computation.java

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+package StringAddCalculator.domain;
+
+import java.util.Arrays;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class Computation {
+    public int getNumber(String s) {
+
+        String sum = s;
+        if(s == null || s.isEmpty()) {
+            return 0;
+        }
+
+        Matcher m = Pattern.compile("//(.)\\\\n(.*)").matcher(s);
+        if(m.find()) {
+            String customDelimiter = m.group(1);
+            String[] tokens = m.group(2).split(customDelimiter);
+
+            sum = String.valueOf(addNumber(tokens));
+            return Integer.parseInt(String.valueOf(sum));
+        }
+
+        return addNumber(s.split(",|:"));
+    }
+
+    static int addNumber(String[] arr) {
+        return Arrays.stream(arr).map(item -> Integer.parseInt(item)).reduce(0, (a, b) -> a+b);
+    }
+}

src/main/java/StringAddCalculator/view/InputView.java

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+package StringAddCalculator.view;
+
+import java.util.Scanner;
+
+public class InputView {
+    Scanner scanner = new Scanner(System.in);
+
+    public String askAddNumber() {
+        System.out.println("입력해주세요");
+        String AddText = scanner.nextLine();
+        return AddText;
+    }
+
+}

src/test/java/StringAddCalculator/StringCalculatorTest.java

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+package StringAddCalculator;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+
+import StringAddCalculator.controller.StringAddCalculator;
+import StringAddCalculator.domain.Computation;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+public class StringCalculatorTest {
+    private Computation computation;
+
+    @BeforeEach
+    void setUp() {
+        computation = new Computation();
+    }
+
+    @DisplayName("널이나 빈값체크")
+    @Test
+    public void splitAndSum_null_또는_빈문자() {
+        int result = computation.getNumber(null);
+        assertEquals(0, result);
+
+        result = computation.getNumber("");
+        assertEquals(0, result);
+    }
+
+    @DisplayName("숫자 하나 체크")
+    @Test
+    public void splitAndSum_숫자하나() throws Exception {
+        int result = computation.getNumber("1");
+        assertThat(result).isEqualTo(1);
+    }
+
+    @DisplayName("쉼표 구분문자 체크")
+    @Test
+    public void splitAndSum_쉼표구분자() throws Exception {
+        int result = computation.getNumber("1,2");
+        assertThat(result).isEqualTo(3);
+    }
+
+    @DisplayName("쉼표 또는 콜론 구분자")
+    @Test
+    public void splitAndSum_쉼표_또는_콜론_구분자() throws Exception {
+        int result = computation.getNumber("1,2:3");
+        assertThat(result).isEqualTo(6);
+    }
+
+    @DisplayName("구분자")
+    @Test
+    public void splitAndSum_custom_구분자() throws Exception {
+        int result = computation.getNumber("//;\\n1;2;3");
+        assertThat(result).isEqualTo(6);
+    }
+}