JavaFX Application create stop watch

import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.text.Font;
import javafx.scene.text.Text;
import javafx.stage.Stage;
import javafx.util.Duration;

public class Main extends Application {
   protected Button btStart = new Button("Start");
   protected Button btClear = new Button("Clear");

   @Override//from   w ww  .j a va 2s  .  c  om
   public void start(Stage primaryStage) {
      // Create a hbox for buttons
      HBox paneForButtons = new HBox(5);
      paneForButtons.setAlignment(Pos.CENTER);
      paneForButtons.getChildren().addAll(btStart, btClear);

      // Create a Stopwatch
      StopWatch stopWatch = new StopWatch();

      // Create a border pane
      BorderPane pane = new BorderPane();
      pane.setBottom(paneForButtons);
      pane.setCenter(stopWatch);

      // Create and register handlers
      btStart.setOnAction(e -> {
         if (btStart.getText().equals("Start") || btStart.getText().equals("Resume")) {
            stopWatch.start();
            btStart.setText("Pause");
         } else {
            stopWatch.pause();
            btStart.setText("Resume");
         }
      });

      btClear.setOnAction(e -> {
         stopWatch.clear();
      });

      // Create a scene and place it in the stage
      Scene scene = new Scene(pane);
      primaryStage.setTitle("java2s.com");
      primaryStage.setScene(scene);
      primaryStage.show();
   }
}

class StopWatch extends BorderPane {
   private Text tTime;
   private Button btControl;
   private Button btClear;
   private int hours;
   private int minutes;
   private int seconds;
   private Timeline timeline;

   public StopWatch() {
      hours = 0;
      minutes = 0;
      seconds = 0;

      // set up the time display
      tTime = new Text();
      tTime.setFont(Font.font("SansSerif", 50));
      setTime();

      // set up the control buttons
      btControl = new Button("Start");
      btClear = new Button("Clear");

      btControl.setOnAction(e -> {
         String text = btControl.getText();
         if (text.equals("Start") || text.equals("Resume")) {
            btControl.setText("Pause");
            if (text.equals("Start")) {
               start();
            } else {
               resume();
            }
         } else {
            btControl.setText("Resume");
            pause();
         }
      });

      btClear.setOnAction(e -> {
         btControl.setText("Start");
         clear();
      });

      // lay out the UI
      HBox buttonBox = new HBox(10);
      buttonBox.getChildren().addAll(btControl, btClear);
      buttonBox.setAlignment(Pos.CENTER);

      setCenter(tTime);
      setBottom(buttonBox);
      setMargin(tTime, new Insets(20, 50, 20, 50));
   }

   public void start() {
      KeyFrame kf = new KeyFrame(Duration.millis(1000), e -> {
         seconds++;
         setTime();
      });

      timeline = new Timeline(kf);
      timeline.setCycleCount(Timeline.INDEFINITE);
      timeline.play();
   }

   public void pause() {
      timeline.pause();
   }

   public void resume() {
      timeline.play();
   }

   public void clear() {
      timeline.stop();
      hours = 0;
      minutes = 0;
      seconds = 0;
      setTime();
   }

   public void setTime() {
      // flip 60 seconds over to a minute
      if (seconds == 60) {
         seconds = 0;
         minutes++;
      }

      // flip 60 minutes over to an hour
      if (minutes == 60) {
         minutes = 0;
         hours++;
      }

      // ensure that values < 10 are padded with a 0
      String h = hours >= 10 ? String.valueOf(hours) : "0" + String.valueOf(hours);
      String m = minutes >= 10 ? String.valueOf(minutes) : "0" + String.valueOf(minutes);
      String s = seconds >= 10 ? String.valueOf(seconds) : "0" + String.valueOf(seconds);

      tTime.setText(h + ":" + m + ":" + s);
   }
}