code: private static boolean validateSyntax(List<String> parts) {
      final int lastIndex = parts.size() - 1;
  
      // Validate the last part specially, as it has different syntax rules.
  
      if (!validatePart(parts.get(lastIndex), true)) {
        return false;
      }
  
      for (int i = 0; i < lastIndex; i++) {
        String part = parts.get(i);
        if (!validatePart(part, false)) {
          return false;
        }
      }
  
      return true;
    }
docs: Validation method used by {@code from} to ensure that the domain name is syntactically valid
  according to RFC 1035.
  
  @return Is the domain name syntactically valid?