support of comparator in SFTP-Adapter

I've implemented a OlderFirstComparator for the SFTP-transporter similar to the File-implementation.
Same could be probably done for FTP.
Map.Entry is not the best abstraction for this. I would create a new class which represents a file's properties. This would not only provide a better layer of abstraction (which would decouple you from the actual ftp client), but would also allow the creation of a larger set of exchangeable comparators which take others attributes in count (for example, directories first, etc).