protected FileWatchdog(String filename) 
{
  
    this.filename = filename;
    file = new File(filename);
    setDaemon(true);
    checkAndConfigure();
}

 protected  void checkAndConfigure() 
{
    boolean fileExists;
    try {
      fileExists = file.exists();
    } catch(SecurityException  e) {
      LogLog.warn("Was not allowed to read check file existance, file:["+
		  filename+"].");
      interrupted = true; // there is no point in continuing
      return;
    }
    if(fileExists) {
      long l = file.lastModified(); // this can also throw a SecurityException
      if(l  > lastModif) {           // however, if we reached this point this
	lastModif = l;              // is very unlikely.
	doOnChange();
	warnedAlready = false;
      }
    } else {
      if(!warnedAlready) {
	LogLog.debug("["+filename+"] does not exist.");
	warnedAlready = true;
      }
    }
}

 abstract protected  void doOnChange()

 public  void run() 
{
    
    while(!interrupted) {
      try {
	    Thread.sleep(delay);
      } catch(InterruptedException e) {
	// no interruption expected
      }
      checkAndConfigure();
    }
}

 public  void setDelay(long delay) 
{
    this.delay = delay;
}

Set the delay to observe between each check of the file changes.