code: @Nullable
      public static String trimToNull(@Nullable String string) {
          return Optional.ofNullable(string)
                  .map(String::trim)
                  .filter(StringUtils::isNotEmpty)
                  .orElse(null);
      }
docs: Trims the supplied string. If the string is empty or null before or after
  trimming, null is returned.
  
  @param string the string to trim
  @return the trimmed string or null