public class Ball extends Disk
{
  private double dx;
  private double dy;

  public Ball( int x, int y, int r, double dx, double dy )
  {
    super(x, y, r);
    this.dx = dx;
    this.dy = dy;
  }

  public void move()
  {
    region().translate( (int) dx, (int) dy );
  }

  protected void setMotion( double ndx, double ndy )
  {
    dx = ndx;
    dy = ndy;
  }

  protected double xMotion()
  {
    return dx;
  }

  protected double yMotion()
  {
    return dy;
  }
}