Why is the button not showing in javaFX?

Question

JavaFX

Help me please. Just an empty window is obtained, the button does not display. I am doing in intellij idea, java 8 is installed. Here is the code:

package com.company;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.stage.Stage;

import java.io.IOException;


public class Main extends Application {
  
    public static void main(String[] args) throws IOException {
        Application.launch(args);
}
 @Override
    public void start(Stage primaryStage) throws Exception {
        Group group = new Group();
        Scene scene = new Scene(group, 600, 600);
        primaryStage.setTitle("Судоку");
        primaryStage.setScene(scene);
        primaryStage.show();

        Button play = new Button("Play");
        play.setPrefWidth(80);
        play.setOnAction(new EventHandler<ActionEvent>() {

            @Override
            public void handle(ActionEvent event) {
                TableFactory tablefactory = new TableFactory();
                int[][] board = tablefactory.generateBoard(9);
                tablefactory.printTheBoard(board);
            }
        });
     }

Answer 1

That's right, you didn't place the button in any container.