class HexString {

    public static long toLong(String value) {
        String[] octets = value.split(":");
        if (octets.length > 8) {
            throw new NumberFormatException("Input string is too big to fit in long: " + value);
        }
        long l = 0;
        for (String octet: octets) {
            if (octet.length() > 2) {
                throw new NumberFormatException(
                        "Each colon-separated byte component must consist of 1 or 2 hex digits: " + value);
            }
            short s = Short.parseShort(octet, 16);
            l = (l << 8) + s;
        }
        return l;
    }

    private  HexString();

}