final public function validateIdentifier($identifier)
    {
        $this->stringHelper->validate($identifier);

        if (strpos($identifier, '.') !== false) {
            throw new InvalidIdentifierException('Error: Identifier cannot contain period characters');
        }

        // Use regular expression to search for characters that are digits
        // Regex is true when there are  0-n non-digits chars and then one digit
        // (it does not matter what is behind the digit)
        if (preg_match('/(\D*)\d/', $identifier) === 1) {
            throw new InvalidIdentifierException('Error: Identifier cannot contain any digits');
        }

        $this->validateIdentifierMore($identifier);
    }