vrotaru

    private static String convert(int digit, String one, String half, String ten)     {
    switch(digit) {
    case 0: return "";
    case 1: return one;
    case 2: return one + one;
    case 3: return one + one + one;
    case 4: return one + half;
    case 5: return half;
    case 6: return half + one;
    case 7: return half + one + one;
    case 8: return half + one + one + one;
    case 9: return one + ten;
    default:
    throw new IllegalArgumentException("Digit out of range 0-9: " + digit);
    }
    }

    public static String convert(int n) {
    if (n > 3000) {
    throw new IllegalArgumentException("Number out of range 0-3000: " + n);
    }

    return convert(n / 1000, "M", "", "") + 
        convert((n / 100) % 10, "C", "D", "M") +
        convert((n / 10) % 10, "X", "L", "C") +
                convert(n % 10, "I", "V", "X");
}