@Override
    protected @Nullable JComponent createNorthPanel() {
      PanelGridBuilder builder = UI.PanelFactory.grid();
      builder.add(UI.PanelFactory.panel(mySubclassButton).withLabel(JavaBundle.message("label.implementation")))
             .add(UI.PanelFactory.panel(myProviderButton));
      if (myRootDirCombo.getModel().getSize() > 1) {
        builder.add(UI.PanelFactory.panel(myRootDirCombo).withLabel(CommonBundle.message("label.source.root") + ":"));
      }
      return builder.createPanel();
    }
@Override
    protected @Nullable JComponent createNorthPanel()