backend.addListener(PresenceListener.class, this);
backend.addListener(StatusChangeListener.class, this);
backend.addListener(PreferenceListener.class, this);
RosterTreeModel model = new RosterTreeModel();
backend.addListener(RosterListener.class, model);
TreeModel offlineModel=model;
TreeModel onlineModel=model;
if (UIManager.getLookAndFeel().isNativeLookAndFeel()) {