问我怎样才能得到正在运行的舞台呢？Javafx

EN

public class Principal extends Application {

private ArrayList<Stage> listaScene = new ArrayList<>();

private static Principal principal;

public static Principal getPrincipal() {
if (principal == null) {
    principal = new Principal();
}
return principal;
}

public void createScene() throws IOException, Exception {

//metodo para cada ventana la controladora
Stage primaryStageAutomatico = ControllerAutoExp.initialicePage();
Principal.getPrincipal().getListScene().add(primaryStageAutomatico);

}

@Override
public void start(Stage primaryStage) throws Exception {
System.setProperty("glass.accessible.force", "false");
try {
      createScene();
      ControllerManejarDatos.initialicePage();

} catch (IOException ex) {
    Logger.getLogger(Principal.class.getName()).log(Level.SEVERE, null,       ex);
    ErrorLogger.recordError(ex);
}
}

public void showAuto(ActionEvent event) {

try {

    boolean find = false;
    int i = 0;        
    while (find == false && i < listaScene.size()) {
        if (listaScene.get(i).getTitle().equals("Ventana Auto")) {
            if (!listaScene.get(i).isShowing()) {
               Stage primaryStageLista =   ControllerAutoExp.initialicePage();                      
               listaScene.add(i, primaryStageLista);
                  listaScene.get(i).initModality(Modality.APPLICATION_MODAL);                     
               listaScene.get(i).show();                       
            } else {
                listaScene.get(i).close();
                listaScene.get(i).initModality(Modality.APPLICATION_MODAL);
                listaScene.get(i).show();
            }
            find = true;
        } else {
            i++;
        }
    }

  } catch (Exception e) {
    try {
        ErrorLogger.recordError(e);
    } catch (IOException ex) {
        Logger.getLogger(Principal.class.getName()).log(Level.SEVERE, null, ex);
    }
  }
}