javafx.stage.Popup as JOptionPane

It is easy to create JoptionPane equivalent in Javafx2.0.
Here is a custom Component:

import javafx.stage.*; 
import javafx.scene.*;
import javafx.scene.paint.Color;
import javafx.scene.control.*;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;

public class ModalDialog {
    Button Button b1,b2;
    public ModalDialog(final Stage stg) {

            final Stage dialog = new Stage();
            dialog.setTitle("Confirm Before Exit");
            dialog.setResizable(false);
          // dialog.initOwner(Demoslide.getPrimaryStage());
            dialog.initModality(Modality.APPLICATION_MODAL);

            FlowPane buttons = new FlowPane(10,10);
            buttons.setAlignment(Pos.CENTER);
            Button yes = new Button("Yes");
           Button no = new Button("No");
            buttons.getChildren().addAll(yes, no);
            VBox box = new VBox();
            box.setAlignment(Pos.CENTER);
            box.setSpacing(10);
            box.getChildren().addAll(new Label("Successfully login "), buttons);
             Scene s = new Scene(box);
            dialog.setScene(s);
            dialog.show();
         }
      
      
    }