Why FtpFile#listFiles() require that the file list is ordered?

[Andrea Francia]

   /**
    * List file objects. If not a directory or does not exist, null will be
    * returned. Files must be returned in alphabetical order.
    */
   FtpFile[] listFiles();

Why is needed to returns files ordered in alphabetical order?
I don't want reorder my files.

--
Andrea Francia
http://andreafrancia.blogspot.com/2008/07/colinux-linux-dentro-windows.html