From TeamDev Ltd.:
JxFileWatcher is a cross-platform library that provides convenient Java API for monitoring file system events. It is available for Windows, Linux, and Mac OS X platforms and supports both 32 and 64-bit versions of these OS. Basic file operations include watch for creation, renaming or removal of files and subfolders within the specified folder, file access monitoring - you will be able to receive notifications about events when access or modification date is changed, and watch properties change. These are System, Hidden and Read only and Archived attributes for Windows platforms. It supports different file systems and always uses the best algorithm for monitoring file system events in a specified watching directory.