JavaFX KeyFrame create spin animation

import javafx.animation.Animation;
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.control.Slider;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Arc;
import javafx.scene.shape.ArcType;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;
import javafx.util.Duration;

public class Main extends Application {
   public static void main(String[] args) {
      Application.launch(args);//w  w w . ja  v a 2s  .c  o m
   }

   @Override
   public void start(Stage primaryStage) throws Exception {
      FanPane pane = new FanPane(100);
      BorderPane borderPane = new BorderPane(pane);
      borderPane.setTop(pane.hButtons);
      borderPane.setBottom(pane.scrollPane);
      primaryStage.setScene(new Scene(borderPane));
      primaryStage.setTitle("Fan");
      primaryStage.show();
   }

}

class FanPane extends Pane {

   private Circle c;
   private Arc[] blades = new Arc[4];
   private double increment = 1;

   // Buttons
   Button playPause = new Button("Play/Pause");
   // Button resume = new Button("Resume");
   Button increase = new Button("Increase");
   Button decrease = new Button("Decrease");
   Button reverse = new Button("Reverse");

   // HBox hButtons = new HBox(pause,resume,increase,decrease, reverse);
   HBox hButtons = new HBox(playPause, increase, decrease, reverse);
   Timeline fanTimeline;
   // ScrollBar mScrollBar = new ScrollBar();

   Slider mSlider = new Slider();
   HBox scrollPane = new HBox(mSlider);

   FanPane(double radius) {
      double w = radius * 4;
      double h = radius * 2;

      setMinWidth(w);
      setMinHeight(h + radius);
      c = new Circle(w / 2, h / 2 + (radius / 2), radius, Color.TRANSPARENT);
      c.setStroke(Color.BLACK);

      double bladeRadius = radius * 0.9;
      for (int i = 0; i < blades.length; i++) {
         blades[i] = new Arc(c.getCenterX(), c.getCenterY(), // center point
               bladeRadius, bladeRadius, // X and Y radius
               (i * 90) + 30, 35); // start angle and length
         blades[i].setFill(Color.RED);
         blades[i].setType(ArcType.ROUND);
      }

      getChildren().addAll(c);
      getChildren().addAll(blades);

      KeyFrame keyFrame = new KeyFrame(Duration.millis(10), e -> spin());

      fanTimeline = new Timeline(keyFrame);
      fanTimeline.setCycleCount(Timeline.INDEFINITE);

      // Buttons pause, resume, increase, decrease, reverse
      playPause.setOnAction(e -> {
         if (fanTimeline.getStatus() == Animation.Status.RUNNING) {
            fanTimeline.pause();
         } else {
            fanTimeline.play();
         }
      });

      increase.setOnAction(e -> {
         fanTimeline.setRate(fanTimeline.getCurrentRate() + 1);
         mSlider.setValue(fanTimeline.getCurrentRate());
      });

      decrease.setOnAction(e -> {
         fanTimeline.setRate((fanTimeline.getCurrentRate() - 1 < 0) ? 0 : fanTimeline.getCurrentRate() - 1);
         mSlider.setValue(fanTimeline.getCurrentRate());

      });
      mSlider.setMin(0);
      mSlider.setMax(35);
      mSlider.valueProperty().addListener(e -> {
         final double direction = (fanTimeline.getCurrentRate() >= 0) ? 1 : -1;
         fanTimeline.setRate(mSlider.getValue() * direction);
      });
      mSlider.setMinWidth(200);
      scrollPane.setAlignment(Pos.CENTER);
      scrollPane.setPadding(new Insets(5));

      reverse.setOnAction(e -> increment *= -1);
      hButtons.setSpacing(10);
      hButtons.setAlignment(Pos.CENTER);
      hButtons.setPadding(new Insets(5, 5, 5, 5));

   }

   private void spin() {
      for (Arc blade : blades) {
         double prevStartAngle = blade.getStartAngle();
         blade.setStartAngle(prevStartAngle - increment);
      }
   }

}