docs: @Nullable
    private static String _getFilename (@Nullable final String sContentDisposition)
    {
      String sFilename = null;
      if (sContentDisposition != null)
      {
        final String sContentDispositionLC = sContentDisposition.toLowerCase (Locale.US);
        if (sContentDispositionLC.startsWith (RequestHelper.FORM_DATA) ||
            sContentDispositionLC.startsWith (RequestHelper.ATTACHMENT))
        {
          // Parameter parser can handle null input
          final ICommonsMap <String, String> aParams = new ParameterParser ().setLowerCaseNames (true)
                                                                             .parse (sContentDisposition, ';');
          if (aParams.containsKey ("filename"))
          {
            sFilename = aParams.get ("filename");
            if (sFilename != null)
            {
              sFilename = sFilename.trim ();
            }
            else
            {
              // Even if there is no value, the parameter is present,
              // so we return an empty file name rather than no file
              // name.
              sFilename = "";
            }
          }
        }
      }
      return sFilename;
    }