JavaFX Circle set center

import javafx.application.Application;
import javafx.scene.Scene;
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;

public class Main extends Application {
  private static final int RADIUS = 100;
  private static final int GAP = 10;
  @Override/*from   ww  w  .j  a v a 2 s  . c o  m*/
  public void start(Stage primaryStage) throws Exception {

    Pane pane = new Pane();
    int x = RADIUS + GAP;
    int y = RADIUS + GAP;

    for (int i = 0; i < 2; i++) {

      // drawing a 2 Circles in each row
      for (int j = 0; j < 2; j++) {
        // create circle
        Circle c = new Circle(RADIUS);
        c.setCenterX(x);
        c.setCenterY(y);
        c.setStroke(Color.BLACK);
        c.setFill(Color.WHITE);
        pane.getChildren().add(c);

        // create 4 arcs in each circle with 90 degree increment
        for (int k = 30; k < 360; k += 90) {
          Arc arc = new Arc(x, y, RADIUS - 15, RADIUS - 15, k, 30);
          arc.setFill(Color.BLACK);
          arc.setType(ArcType.ROUND);
          pane.getChildren().add(arc);
        }

        x += RADIUS * 2 + GAP;
      }
      // reset center for the next row
      x = RADIUS + GAP;
      y += RADIUS * 2 + GAP;
    }

    Scene scene = new Scene(pane, 425, 425);
    primaryStage.setScene(scene);
    primaryStage.setTitle("Fans");
    primaryStage.show();
  }

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