import javafx.application.Application;
//import javafx.stage.Modality;
import javafx.stage.Stage;

public class App extends Application {
    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) {
          Stage stage = new Stage();
        //stage.initModality(Modality.APPLICATION_MODAL);
        //stage.initModality(Modality.WINDOW_MODAL);
        //stage.initModality(Modality.NONE);
        stage.initOwner(primaryStage);
        stage.setTitle("Test App");

        stage.setX(500);
        stage.setY(500);
        stage.setWidth(200);
        stage.setHeight(100);

        stage.showAndWait();
    }
}