Watching a Directory for Modifications in Java 7

NIO 2.0 in Java 7 added support for directory change notification known as a watch service. It lets you receive notifications, when a directory is modified. There are six steps needed to set up a watch service.

  • Creating a watch service
  • Registering a directory with the watch service
  • Retrieving a watch key from the watch service queue
  • Processing the events that occurred on the registered directory
  • Resetting the watch key after processing the events
  • Closing the watch service

A watch service is an instance of the WatchService interface. You can create a watch service for the default file system as:

WatchService ws = FileSystems.getDefault().newWatchService();

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