for (Node circle : circles.getChildren()) {
timeline.getKeyFrames().addAll(
new KeyFrame(Duration.ZERO, // set start position at 0
new KeyValue(circle.translateXProperty(),
random() * 800),
new KeyValue(circle.translateYProperty(),
random() * 600)),
new KeyFrame(new Duration(40000), // set end position at 40s
new KeyValue(circle.translateXProperty(),
random() * 800), new KeyValue(circle
.translateYProperty(), random() * 600)));