Kata de enero

soyangel/StringCalculator.java

@@ -0,0 +1,84 @@
+import java.util.regex.Pattern;
+
+public class StringCalculator
+{
+
+	private static final String NEGATIVES_MESSAGE = "Negatives not allowed";
+	private static final String NUMBER_SEPARATOR = ",|\n";
+	private static final String PREFIX_CUSTOM_DELIMITER = "//";
+
+	public static int calculate(String numbers) throws Exception
+	{
+		int[] operands = extractNumbers(numbers);
+		return addNumbers(operands);
+	}
+
+	private static int[] extractNumbers(String numbers)
+	{
+		String[] operands = splitArray(numbers);
+		return stringArrayToIntArray(operands);
+	}
+
+	private static String[] splitArray(String numbers)
+	{
+		if (numbers.equals(""))
+			return new String[0];
+
+		String delimiter = getDelimiter(numbers);
+		numbers = removeDelimiterDefinition(numbers);
+		return numbers.split(delimiter);
+	}
+
+	private static String removeDelimiterDefinition(String numbers)
+	{
+		if (numbers.startsWith(PREFIX_CUSTOM_DELIMITER))
+			return numbers.replaceFirst(PREFIX_CUSTOM_DELIMITER + ".\n", "");
+		else
+			return numbers;
+	}
+
+	private static String getDelimiter(String numbers)
+	{
+		if (numbers.startsWith(PREFIX_CUSTOM_DELIMITER))
+			return extractDeclaredDelimiter(numbers);
+		else
+			return NUMBER_SEPARATOR;
+	}
+
+	private static String extractDeclaredDelimiter(String numbers)
+	{
+		String delimiter = numbers.split("//|\n")[1];
+		return Pattern.quote(delimiter);
+	}
+
+	private static int addNumbers(int[] numbers) throws Exception
+	{
+		int sum = 0;
+		String negativeNumbers = "";
+		for (int number : numbers)
+		{
+			if (number < 0)
+				negativeNumbers += " " + number;
+			else
+				sum += number;
+		}
+
+		if (negativeNumbers.isEmpty())
+			return sum;
+		else
+			throw new Exception(NEGATIVES_MESSAGE + negativeNumbers);
+	}
+
+	private static int[] stringArrayToIntArray(String[] operands)
+	{
+		int[] result = new int[operands.length];
+
+		for (int i = 0; i < operands.length; i++)
+		{
+			result[i] = Integer.parseInt(operands[i]);
+		}
+
+		return result;
+	}
+
+}

soyangel/StringCalculatorTest.java

@@ -0,0 +1,90 @@
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+public class StringCalculatorTest
+{
+	@Test
+	public void canCalculate0Numbers() throws Exception
+	{
+		assertEquals(0, StringCalculator.calculate(""));
+	}
+
+	@Test
+	public void canCalculate1Number() throws Exception
+	{
+		assertEquals(0, StringCalculator.calculate("0"));
+		assertEquals(1, StringCalculator.calculate("1"));
+	}
+
+	@Test
+	public void canCalculate2Numbers() throws Exception
+	{
+		assertEquals(1, StringCalculator.calculate("0,1"));
+		assertEquals(3, StringCalculator.calculate("1,2"));
+	}
+
+	@Test
+	public void canCalculateUnknownAmountOfNumbers() throws Exception
+	{
+		assertEquals(55, StringCalculator.calculate("0,1,2,3,4,5,6,7,8,9,10"));
+	}
+
+	@Test
+	public void canUseNewlineAsSeparator() throws Exception
+	{
+		assertEquals(1, StringCalculator.calculate("0\n1"));
+		assertEquals(3, StringCalculator.calculate("0\n1,2"));
+	}
+
+	@Test
+	public void canSupportDefinableDelimiters() throws Exception
+	{
+		assertEquals(10, StringCalculator.calculate("//;\n1;2;4;3"));
+		assertEquals(10, StringCalculator.calculate("//.\n1.2.4.3"));
+		assertEquals(21, StringCalculator.calculate("//*\n5*6*10"));
+	}
+
+	@Test
+	public void mustThrowExceptionOnNegatives() throws Exception
+	{
+		try
+		{
+			StringCalculator.calculate("0\n-1");
+			fail("Exception expected but not thrown");
+		}
+		catch (Exception e)
+		{
+			assertEquals("Negatives not allowed -1", e.getMessage());
+		}
+	}
+
+	@Test
+	public void mustThrowExceptionOnNegativesWithPrefix() throws Exception
+	{
+		try
+		{
+			StringCalculator.calculate("//*\n5*-6*10");
+			fail("Exception expected but not thrown");
+		}
+		catch (Exception e)
+		{
+			assertEquals("Negatives not allowed -6", e.getMessage());
+		}
+	}
+
+	@Test
+	public void mustThrowExceptionOnSeveralNegativesWithPrefix() throws Exception
+	{
+		try
+		{
+			StringCalculator.calculate("//*\n5*-6*-10*-2");
+			fail("Exception expected but not thrown");
+		}
+		catch (Exception e)
+		{
+			assertEquals("Negatives not allowed -6 -10 -2", e.getMessage());
+		}
+	}
+
+}