public boolean isFree(XY xy) {
        if (
                (xy.getX() < 0) ||
                        (xy.getX() >= this.width) ||
                        (xy.getY() < 0) ||
                        (xy.getY() >= this.height) ||
                        (this.get(xy) != null)

                ) {
            return false;
        }

        return true;
    }