public Ring(AbstractCircle outCircle, AbstractCircle inCircle, int centreX, int centreY)
{
_centreX = centreX;
_centreY = centreY;
_outCircle = outCircle;
_inCircle = inCircle;
}
public Ring(AbstractCircle outCircle, AbstractCircle inCircle) : this(outCircle, inCircle, 0, 0)
{
}