else if (!file.exists () && users.size () > 0) users.clear ();
    public boolean authenticate (String username, String pw) {	if (file.exists() && file.lastModified () > lastRead)	    readFile ();	String realpw = users.getProperty (username);	if (realpw != null) {	    // check if password matches	    String cryptpw = Crypt.crypt (realpw, pw);	    return realpw.equals (cryptpw);	} else {	    if (parentFile != null)	        return parentFile.authenticate (username, pw);	}	return false;    }