Java I/O How to - Monitor file system for delete, create and modify events

Question

We would like to know how to monitor file system for delete, create and modify events.

Answer

import java.io.IOException;
import java.nio.file.FileSystem;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardWatchEventKinds;
import java.nio.file.WatchEvent;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
//from w ww. jav  a  2s . c om
public class Main {
  public static void main(String[] args) throws Exception {
    FileSystem fileSystem = FileSystems.getDefault();
    WatchService watchService = fileSystem.newWatchService();
    Path directory = Paths.get("/home/docs");
    WatchEvent.Kind<?>[] events = { StandardWatchEventKinds.ENTRY_CREATE,
        StandardWatchEventKinds.ENTRY_DELETE,
        StandardWatchEventKinds.ENTRY_MODIFY };
    directory.register(watchService, events);
    while (true) {
      System.out.println("Waiting for a watch event");
      WatchKey watchKey = watchService.take();
      System.out.println("Path being watched: " + watchKey.watchable());
      if (watchKey.isValid() == false) {
        return;
      }
      for (WatchEvent<?> event : watchKey.pollEvents()) {
        System.out.println("Kind: " + event.kind());
        System.out.println("Context: " + event.context());
        System.out.println("Count: " + event.count());
        System.out.println();
      }
      boolean valid = watchKey.reset();
      System.out.println(valid);

    }
  }
}