public void place(Sign sign, int col, int row) throws BoardFieldNotEmptyException {
        if (col < 0 || col > 2 || row < 0 || row > 2) {
            throw new ArrayIndexOutOfBoundsException();
        }
        if (b[col][row] != Sign.EMPTY) {
            throw new BoardFieldNotEmptyException();
        }
        b[col][row] = sign;
    }