code: public void list(String filter, String modifier, DataSink sink)
          throws ServerException, ClientException, IOException {
          String arg = null;
  
          if (modifier != null) {
              arg = modifier;
          }
          if (filter != null) {
              arg = (arg == null) ? filter : arg + " " + filter;
          }
  
          Command cmd = new Command("LIST", arg);
  
          performTransfer(cmd, sink);
      }
docs: Performs directory listing and writes the result
  to the supplied data sink.
  This method is allowed in ASCII mode only.
  
  <br><b>Note</b>: <i>
  Please keep in mind that the ftp server might not
  recognize or support all the different modifiers or filters.
  In fact, some servers such as GridFTP server distributed with
  GT 4.0.0 does not support any modifiers or filters
  (strict RFC 959 compliance).
  It is strongly recommended to use {@link #mlsd(String,DataSink)
  mlsd()} function instead.</i>
  
  @param filter remote list command file filter, eg. "*"
  @param modifier remote list command modifier, eg. "-d"
  @param sink data destination