To reproduce run following code and push button

public class JavaFX extends Application {

   
    public static void main(String[] args) {
        launch(args);
    }
    
    @Override
    public void start(Stage primaryStage) {
        Button btn = new Button();
        btn.setContextMenu(new ContextMenu(new CheckMenuItem("Hello")));
        btn.setText("Hello World'");
        
        
        StackPane root = new StackPane();
        root.getChildren().add(btn);
        primaryStage.setScene(new Scene(root, 300, 250));
        primaryStage.show();
    }
}