Some ftp server hide files from their users.
You can view them by issuing a "LIST -a" command.
I propose to add the method
FTPClient.setListHiddenFiles(boolean listHiddenFiles)
and if it is set to add a " -a" in to the list command in method
FTPClient.listFiles(FTPFileListParser parser, String pathname)
I'll prepare a patch if there is consens.
Thanks to Sylvain Perez for pointing this out.