if (! isValidViewMode(viewMode)) {
if ((viewMode != null) && (! isValidViewMode(viewMode))) {
  public final void setViewMode(String viewMode) throws IllegalArgumentException {    if (! isValidViewMode(viewMode)) {      throw new IllegalArgumentException("\"" + viewMode + "\" is not a valid view mode; " +                                         "it must be one of " + VIEWMODES);    }    // set the view mode    $viewMode = viewMode;  }