Clickable

Clickable.java

import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;


public class Main extends Application {
    @Override
    public void start(Stage primaryStage) throws Exception {
        Button button1 = new Button("Hey");
        VBox box = new VBox(10, button1);
        button1.setOnAction(event -> {
            Button btn = new Button();
            btn.setText("Say 'Hello World'");
            btn.setOnAction(event1 -> System.out.println("Hello World!"));
            box.getChildren().add(btn);
        });

        box.setAlignment(Pos.CENTER);
        Scene scene = new Scene(box, 200, 200);
        primaryStage.setScene(scene);
        primaryStage.show();
    }
}