public class Dialog<T> extends Stage{

    private FXMLLoader loader;

    public Dialog(String fxml, String actionId){
        initStyle(StageStyle.UTILITY);
        initModality(Modality.APPLICATION_MODAL);

        Scene scene = null;
        try {
            loader = new FXMLLoader(getClass().getResource(fxml));
            Pane root = (Pane) loader.load();
            scene = new Scene(root );
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        Button delete = (Button) scene.lookup(actionId);
        delete.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent e) {
                if(onAction()){
                    close();
                }
            }
        });
        Button cancel = (Button) scene.lookup("#cancel");
        cancel.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent e) {
                close();
            }
        });
        setScene(scene);
    }

    public T getController() {
        return loader.getController();
    }

    public boolean onAction(){
        //Override to implement
        return true;
    }
}

//*********************
                    final Dialog<DeleteController> dialog = new Dialog<DeleteController>("/fxml/DeleteScenario.fxml", "#delete"){
                        @Override
                        public boolean onAction() {
                            behavior.setFormula(backup);
                            //Is this a good way to refresh UI?
                            behaviorFormulaListColumn.setVisible(false);
                            behaviorNameListColumn.setVisible(false);
                            behaviorFormulaListColumn.setVisible(true);
                            behaviorNameListColumn.setVisible(true);
                            return true;
                        }
                    };

                    dialog.setTitle("Warning");
                    dialog.getController().message.setWrapText(true);
                    dialog.getController().message.setText(test);
                    dialog.getController().confirm.setText("Revert");
                    dialog.getController().cancel.setText("Keep");
                    dialog.showAndWait();