SessionScavenger scavenger = _scavenger;
Thread scavenger = _scavenger;
    public void doStop()    	throws Exception	    {        super.doStop();                // Invalidate all sessions to cause unbind events        ArrayList sessions = new ArrayList(_sessions.values());        for (Iterator i = sessions.iterator(); i.hasNext(); )        {            Session session = (Session)i.next();            session.invalidate();        }        _sessions.clear();                // stop the scavenger        SessionScavenger scavenger = _scavenger;        _scavenger=null;        if (scavenger!=null)            scavenger.interrupt();                _loader=null;    }