Try to convert arbitrary length string decimal to string hexadecimal

decimal-to-hex.java

public class Decimal2Hex {

    private static String[] HEX = new String[]{
        "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F"
    };

    public static String convert(final String numberText) {

        final Object[] result   = divideTo16(numberText);
        final String   quotient = (String) result[0];
        final String   hexValue = HEX[(int) result[1]];

        if (quotient.length() < 3) { // It's not rational to parse every quotient
            final int intQuotient = Integer.parseInt(quotient);

            if (intQuotient < 16) {
                return HEX[intQuotient] + hexValue;
            }
        }

        return convert(quotient) + hexValue;
    }

    private static Object[] divideTo16(final String numberText) {

        final Object[] result = divideFragmentTo16(
            numberText, 0, numberText.length() > 1 ? 2 : 1, "", 0
        );

        // Simply removing unnecessary 0 prefix
        String quotient = (String) result[0];

        if (quotient.length() > 1 && quotient.startsWith("0")) {
            quotient = quotient.substring(1);
        }

        return new Object[]{quotient, result[1]};
    }

    private static Object[] divideFragmentTo16(
        final String numberText,
        final int start,
        int stop,
        final String totalQuotient,
        final int reminder
    ) {

        final int    number      = Integer.parseInt(reminder + numberText.substring(start, stop));
        final int    newReminder = number % 16;
        final String quotient    = totalQuotient + number / 16;

        if (stop + 1 > numberText.length()) {
            return new Object[]{
                quotient,
                newReminder
            };
        }

        return divideFragmentTo16(
            numberText, stop, stop + 1, quotient, newReminder
        );
    }
}