Free Java FTP library gives Java developers:

• Extensive FTP functionality.
• Robust and proven - in use in tens of thousands of applications worldwide.
• Java source-code included!
• Open source and free for commercial use (LGPL).
• Downloaded over 200,000 times!

Non-GPL source licenses can be also be purchased.

edtFTPj/PRO adds directory transfers and secure FTP capabilities to edtFTPj, implementing the FTPS and SFTP protocols. From $399.