JavaFX PathTransition animate along arc

import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.shape.Arc;
import javafx.scene.shape.ArcType;
import javafx.scene.shape.Circle;
import javafx.scene.paint.Color;
import javafx.animation.PathTransition;
import javafx.animation.Timeline;
import javafx.util.Duration;

public class Main extends Application {
  @Override//from   ww w . jav a2  s.  co m
  public void start(Stage primaryStage) {
    final double WIDTH = 500.0;
    final double HEIGHT = 500.0;
    final double RADIUS = 200.0;

    Pane pane = new Pane();

    Arc arc = new Arc(WIDTH / 2, HEIGHT / 2, RADIUS, RADIUS, 225, 90);
    arc.setFill(Color.WHITE);
    arc.setStroke(Color.BLACK);
    arc.setType(ArcType.OPEN);

    Circle circle = new Circle(RADIUS / 20);

    PathTransition pt = new PathTransition(Duration.millis(5000),
      arc, circle);
    pt.setCycleCount(Timeline.INDEFINITE);
    pt.setAutoReverse(true);
    pt.play();

    pane.getChildren().addAll(arc, circle);
    pane.setOnMousePressed(e -> pt.pause());
    pane.setOnMouseReleased(e -> pt.play());

    Scene scene = new Scene(pane, WIDTH, HEIGHT);
    primaryStage.setTitle("java2s.com");
    primaryStage.setScene(scene);
    primaryStage.show();
  }

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