/*
     * Note that we allow (in contravention of a strict interpretation of the relevant RFCs) domain
     * parts other than the last may begin with a digit (for example, "3com.com"). It's important to
     * disallow an initial digit in the last part; it's the only thing that stops an IPv4 numeric
     * address like 127.0.0.1 from looking like a valid domain name.
     */

    if (isFinalPart && DIGIT_MATCHER.matches(part.charAt(0))) {

    // contain non-decimal characters.
    int length = end - start;
    if (length <= 0 || length > 3) {
      throw new NumberFormatException();
    }
    // Disallow leading zeroes, because no clear standard exists on
    // whether these should be interpreted as decimal or octal.
    if (length > 1 && ipString.charAt(start) == '0') {
      throw new NumberFormatException();
    }

    // contain non-decimal characters.
    int length = end - start;
    if (length <= 0 || length > 3) {
      throw new NumberFormatException();
    }
    // Disallow leading zeroes, because no clear standard exists on
    // whether these should be interpreted as decimal or octal.
    if (length > 1 && ipString.charAt(start) == '0') {
      throw new NumberFormatException();
    }