return null;
Set s = null;  if (focusTraversalKeys != null) s = focusTraversalKeys[id];  if (s == null && parent != null) s = parent.getFocusTraversalKeys (id);  return s == null ? (KeyboardFocusManager.getCurrentKeyboardFocusManager() .getDefaultFocusTraversalKeys(id)) : s;
  public Set getFocusTraversalKeys(int id)  {    if (id != KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS &&        id != KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS &&        id != KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS &&        id != KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS)      throw new IllegalArgumentException ();    return null;  }