Listener for Files?

Question

Hi
is there a (kind of) Listener I can use to get notified when a File gets changed, i.e. when it's content is changed?
Thanks for your help.

Answer 1

I found an implementaion for such a kind of "File Listener" on the web. It's based on an interface and a class with inner class. Here's the linsting:
public interface FileChangeListener
public void fileChanged(String Filename);
import java.io.*;
import java.util.*;
import java.net.*;
public class FileMonitor
private static final FileMonitor instance = new FileMonitor();
private Timer timer;
private Hashtable timerEntries;
protected FileMonitor()
// Create timer, run timer thread as daemon.
     timer = new Timer(true);
     timerEntries = new Hashtable();
public static FileMonitor getInstance()
return instance;
/** Add a monitored file with a FileChangeListener.
* @param listener listener to notify when the file changed.
* @param fileName name of the file to monitor.
* @param period polling period in milliseconds.
public void addFileChangeListener(FileChangeListener listener, String fileName, long period) throws FileNotFoundException
removeFileChangeListener(listener, fileName);
     FileMonitorTask task = new FileMonitorTask(listener, fileName);
     timerEntries.put(fileName + listener.hashCode(), task);
     timer.schedule(task, period, period);
/** Remove the listener from the notification list.
* @param listener the listener to be removed.
public void removeFileChangeListener(FileChangeListener listener, String fileName)
FileMonitorTask task = (FileMonitorTask) timerEntries.remove(fileName + listener.hashCode());
     if (task != null)
     task.cancel();
protected void fireFileChangeEvent(FileChangeListener listener, String fileName)
     listener.fileChanged(fileName);
class FileMonitorTask extends TimerTask
FileChangeListener listener;
String fileName;
File monitoredFile;
     long lastModified;
public FileMonitorTask(FileChangeListener listener, String fileName) throws FileNotFoundException
     this.listener = listener;
     this.fileName = fileName;
     this.lastModified = 0;
monitoredFile = new File(fileName);
     if (!monitoredFile.exists())
// but is it on CLASSPATH?
     URL fileURL = listener.getClass().getClassLoader().getResource(fileName);
          if (fileURL != null)
          monitoredFile = new File(fileURL.getFile());
          else
          throw new FileNotFoundException("File Not Found: " + fileName);
     this.lastModified = monitoredFile.lastModified();
public void run()
     long lastModified = monitoredFile.lastModified();
     if (lastModified != this.lastModified)
     this.lastModified = lastModified;
          fireFileChangeEvent(this.listener, this.fileName);