gistfile1.java

/* StringCalculator Code Kata - I found my solution as beautiful code, even though i will try to get it better */

public class StringCalculator {

    private static final String DELIMITER = "//";

    public int add(String numbers) {
        if (isNumbersEmpty(numbers)) {
            return 0;
        }
        handleNegativeNumber(numbers);
        if (hasDelimiter(numbers)) {
            if (hasMoreThanOneNumber(numbers, substractDelimiter(numbers))) {
                return addMoreThanTwoNumbers(numbers, substractDelimiter(numbers));
            }
        } else {
            return addMoreThanTwoNumbers(numbers);
        }
        return handleOneNumber(numbers);
    }

    private void handleNegativeNumber(String numbers) {
        if (isNumbersNegative(numbers)) {
            throw new IllegalArgumentException("Negative number not allowed - "
                    + numbers);
        }
    }

    private boolean isNumbersNegative(String numbers) {
        return numbers.contains("-");
    }

    private boolean hasMoreThanOneNumber(String numbers, String delimiter) {
        return numbers.contains(delimiter);
    }

    private int handleOneNumber(String numbers) {
        return Integer.parseInt(numbers);
    }

    private boolean isNumbersEmpty(String numbers) {
        return "".equals(numbers);
    }

    private int addMoreThanTwoNumbers(String numbers, String substractDelimiter) {
        numbers = numbers.substring(4, numbers.length());
        return addNumbers(numbers, substractDelimiter);
    }

    private int addMoreThanTwoNumbers(String numbers) {
        numbers = numbers.replaceAll("\n", ",");
        return addNumbers(numbers, ",");
    }

    private String substractDelimiter(String numbers) {
        return numbers.substring(2, 3);
    }

    private boolean hasDelimiter(String numbers) {
        return numbers.startsWith(DELIMITER);
    }

    private int addNumbers(String numbers, String delimiter) {
        int result = 0;
        for (String number : numbers.split(delimiter)) {
            result += handleOneNumber(number);
        }
        return result;
    }

}