k.attach (att);
if (att != null) key.attach(att);
  public final SelectionKey register (Selector selin, int ops, Object att)    throws ClosedChannelException  {    if (!isOpen ())      throw new ClosedChannelException();    SelectionKey k = null;    AbstractSelector selector = (AbstractSelector) selin;    synchronized (LOCK)      {        k = locate (selector);        if (k != null)          {            k.attach (att);          }        else          {            k = selector.register (this, ops, att);    		            if (k != null)              add (k);          }      }    return k;  }