JavaFX BorderPane create a simple calculator

import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.FlowPane;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

public class Main extends Application {
   @Override// ww  w .j a v a  2s.  co m

   public void start(Stage primaryStage) {
      FlowPane pane = new FlowPane();
      pane.setHgap(2);
      pane.setAlignment(Pos.CENTER);
      TextField tfNumber1 = new TextField();
      TextField tfNumber2 = new TextField();
      TextField tfResult = new TextField();
      tfResult.setEditable(false);
      tfNumber1.setPrefColumnCount(3);
      tfNumber2.setPrefColumnCount(3);
      tfResult.setPrefColumnCount(3);

      pane.getChildren().addAll(new Label("Number 1: "), tfNumber1, new Label("Number 2: "), tfNumber2,
            new Label("Result: "), tfResult);

      // Create four buttons
      HBox hBox = new HBox(5);
      Button btAdd = new Button("Add");
      Button btSubtract = new Button("Subtract");
      Button btMultiply = new Button("Multiply");
      Button btDivide = new Button("Divide");
      hBox.setAlignment(Pos.CENTER);
      hBox.getChildren().addAll(btAdd, btSubtract, btMultiply, btDivide);

      BorderPane borderPane = new BorderPane();
      borderPane.setCenter(pane);
      borderPane.setBottom(hBox);
      BorderPane.setAlignment(hBox, Pos.TOP_CENTER);

      Scene scene = new Scene(borderPane, 250, 150);
      primaryStage.setTitle("java2s.com");
      primaryStage.setScene(scene);
      primaryStage.show();

      btAdd.setOnAction(e -> {
         tfResult.setText(Double.parseDouble(tfNumber1.getText()) + Double.parseDouble(tfNumber2.getText()) + "");
      });

      btSubtract.setOnAction(e -> {
         tfResult.setText(Double.parseDouble(tfNumber1.getText()) - Double.parseDouble(tfNumber2.getText()) + "");
      });

      btMultiply.setOnAction(e -> {
         tfResult.setText(Double.parseDouble(tfNumber1.getText()) * Double.parseDouble(tfNumber2.getText()) + "");
      });

      btDivide.setOnAction(e -> {
         tfResult.setText(Double.parseDouble(tfNumber1.getText()) / Double.parseDouble(tfNumber2.getText()) + "");
      });
   }

   public static void main(String[] args) {
      launch(args);
   }
}