if (filter == null || filter.accept(r))
if (filter == null || filter.accept(r.getMessage()))
   public List delivering(Filter filter)   {      List delivering = new ArrayList();      synchronized (deliveries)      {         for(Iterator i = deliveries.iterator(); i.hasNext(); )         {            Delivery d = (Delivery)i.next();            Routable r = d.getReference();            if (filter == null || filter.accept(r))            {               delivering.add(r);            }         }      }      return delivering;   }