File watcher

WatcherExample.java

import static java.nio.file.StandardWatchEventKinds.*;

import java.io.IOException;
import java.net.URL;
import java.nio.file.FileSystems;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.WatchEvent;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
import java.nio.file.attribute.BasicFileAttributes;

public class WatcherExample {

	public static void main(String args[]) throws IOException, InterruptedException {
		URL classFolder = WatcherExample.class.getClassLoader().getResource(".");
		String monitorPath = classFolder.getFile();
		System.out.println(monitorPath + " is watched");
		watchDir(monitorPath);
	}

	public static void watchDir(String dir) throws IOException,	InterruptedException {
		WatchService service = FileSystems.getDefault().newWatchService();
		Path parent = Paths.get(dir); 
	   
		registerSubDirs(service, parent);
		
		while (true) {
			WatchKey key = service.take(); 
			 
			for (WatchEvent<?> event : key.pollEvents()) {
				System.out.println(event.kind() + ": " + event.context()); 
			}
			boolean valid = key.reset();
			if (!valid) {
				break; // Exit if directory is deleted
			}
		}
	}

	private static void registerSubDirs(final WatchService service, Path parent)
			throws IOException {
		Files.walkFileTree(parent, new SimpleFileVisitor<Path>() {
		        @Override
		        public FileVisitResult preVisitDirectory(Path path, BasicFileAttributes attrs) throws IOException {
		        	path.register(service, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
		          return FileVisitResult.CONTINUE;
		        }
		    });
	}
}