import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuBar;
import javafx.scene.control.MenuItem;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;

public class StageTest extends Application {

    @Override
    public void start(Stage primaryStage) {
        BorderPane root = new BorderPane();

        final Menu fileMenu = new Menu("File");
        fileMenu.getItems().addAll(new MenuItem("New..."), new MenuItem("Open..."));

        root.setTop(new MenuBar(fileMenu));

        Button button = new Button("Move to 0,0");
        button.setOnAction(e -> {
            primaryStage.setX(0);
            primaryStage.setY(0);
        });
        root.setCenter(button);

        Scene scene = new Scene(root, 600, 400);
        primaryStage.setScene(scene);
        primaryStage.show();

        primaryStage.yProperty().addListener((obs, ov, nv) ->
            System.out.println("Stage.y at " + nv + ", was at " + ov));
    }
}