민형 문자열 덧셈 계산기

src/main/java/calculator/CalculatorService.java

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+package calculator;
+
+import java.util.List;
+
+public class CalculatorService {
+
+    public int calculate(String expression) {
+        List<Number> numbers = Splitter.getSplitNumbers(expression);
+
+        Number result = numbers.stream()
+                .reduce(Number::sum)
+                .orElseThrow(() -> new ArithmeticException());
+
+        return result.getValue();
+    }
+}

src/main/java/calculator/Number.java

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+package calculator;
+
+public class Number {
+    private final int value;
+
+    public Number(String value) {
+        this.value = parseString(value);
+    }
+
+    public Number(int value) {
+        this.value = value;
+    }
+
+    public int getValue() {
+        return value;
+    }
+
+    public static Number sum(Number a, Number b) {
+        return new Number(a.getValue() + b.getValue());
+    }
+
+    private int parseString(String value) {
+        validateNumber(value);
+        int result = Integer.parseInt(value);
+
+        if (result < 0) {
+            throw new RuntimeException(String.format("음수가 입력되었습니다. : %s ", result));
+        }
+
+        return result;
+    }
+
+    private void validateNumber(String value) {
+        if (value == null || value.isEmpty()) {
+            throw new RuntimeException("빈 문자열 입니다.");
+        }
+    }
+}

src/main/java/calculator/Splitter.java

@@ -0,0 +1,42 @@
+package calculator;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
+public class Splitter {
+    private static final String COMMON_DELIMITER = "[,:]";
+    private static final Pattern CUSTOM_DELIMITER_PATTERN = Pattern.compile("//(.)\n(.*)");
+    private static final String DEFAULT_NUMBER = "0";
+    private static final int DELIMITER_GROUP = 1;
+    private static final int FORMULA_GROUP = 2;
+
+    public static List<Number> getSplitNumbers(String expression) {
+        if (expression == null || expression.isEmpty()) {
+            return commonSplit(DEFAULT_NUMBER);
+        }
+
+        Matcher matcher = CUSTOM_DELIMITER_PATTERN.matcher(expression);
+        if (matcher.find()) {
+            return customSplit(matcher);
+        }
+
+        return commonSplit(expression);
+    }
+
+    private static List<Number> customSplit(Matcher matcher) {
+        String delimiter = matcher.group(DELIMITER_GROUP);
+        String formula = matcher.group(FORMULA_GROUP);
+        return Arrays.stream(formula.split(delimiter))
+                .map(Number::new)
+                .collect(Collectors.toList());
+    }
+
+    private static List<Number> commonSplit(String expression) {
+        return Arrays.stream(expression.split(COMMON_DELIMITER))
+                .map(Number::new)
+                .collect(Collectors.toList());
+    }
+}

src/test/java/calculator/CalculatorServiceTest.java

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+package calculator;
+
+import org.assertj.core.api.ThrowableAssert;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.NullAndEmptySource;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.junit.jupiter.api.Assertions.*;
+
+class CalculatorServiceTest {
+
+    @DisplayName("기본 구분자로 식 입력시 결과 반환")
+    @Test
+    void name() {
+        String expression = "1,2:3";
+        CalculatorService calculatorService = new CalculatorService();
+        int result = calculatorService.calculate(expression);
+        assertThat(result).isEqualTo(6);
+    }
+
+    @DisplayName("커스텀 구분자로 식 입력시 결과 반환")
+    @Test
+    void name1() {
+        String expression = "//h\n1h2h3";
+        CalculatorService calculatorService = new CalculatorService();
+        int result = calculatorService.calculate(expression);
+        assertThat(result).isEqualTo(6);
+    }
+
+    @DisplayName("1 입력시 1 반환")
+    @Test
+    void name4() {
+        String expression = "1";
+        CalculatorService calculatorService = new CalculatorService();
+        int result = calculatorService.calculate(expression);
+        assertThat(result).isEqualTo(1);
+    }
+
+    @DisplayName("빈 문자열, null 입력시 0")
+    @ParameterizedTest
+    @NullAndEmptySource
+    void name2(String expression) {
+        CalculatorService calculatorService = new CalculatorService();
+        int result = calculatorService.calculate(expression);
+        assertThat(result).isEqualTo(0);
+    }
+
+    @DisplayName("음수 값 있을때 RuntimeExcetion Throw")
+    @Test
+    void name3() {
+        String expression = "1,-2:3";
+        CalculatorService calculatorService = new CalculatorService();
+        assertThatThrownBy(() -> calculatorService.calculate(expression))
+                .isInstanceOf(RuntimeException.class)
+                .hasMessage(String.format("음수가 입력되었습니다. : %s ", -2));
+    }
+}

src/test/java/calculator/NumberTest.java

@@ -0,0 +1,31 @@
+package calculator;
+
+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.EmptySource;
+import org.junit.jupiter.params.provider.NullAndEmptySource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.junit.jupiter.api.Assertions.*;
+
+class NumberTest {
+    @DisplayName("빈 문자열 또는 null일시 RuntimeException Throw")
+    @ParameterizedTest
+    @NullAndEmptySource
+    void name1(String expression) {
+        assertThatThrownBy(() -> new Number(expression))
+                .isInstanceOf(RuntimeException.class)
+                .hasMessage("빈 문자열 입니다.");
+    }
+
+    @DisplayName("음수일시 RuntimeException Throw")
+    @Test
+    void name() {
+        assertThatThrownBy(() -> new Number("-1"))
+                .isInstanceOf(RuntimeException.class)
+                .hasMessage(String.format("음수가 입력되었습니다. : %s ", -1));
+    }
+}

src/test/java/calculator/SplitterTest.java

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+package calculator;
+
+import jdk.nashorn.internal.ir.annotations.Ignore;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class SplitterTest {
+
+    @DisplayName("일반적인 식 입력시 분리된 숫자 List가 반환")
+    @Test
+    void name() {
+        String expression = "1,2:3,4";
+        List<Number> numbers = Splitter.getSplitNumbers(expression);
+        assertThat(numbers.size()).isEqualTo(4);
+    }
+
+    @DisplayName("커스텀 구분자로 입력시 분리된 숫자 List가 반환")
+    @Test
+    void name1() {
+        String expression = "///\n1/2/3/6";
+        List<Number> numbers = Splitter.getSplitNumbers(expression);
+        assertThat(numbers.size()).isEqualTo(4);
+    }
+}