Attribute box in class diagrams

[Nikhilalalalala]

In this question, (and as given in textbook), for the first diagram on the left, there is no blank rectangle for the attributes. However, in Prof Damith's hand drawing of class diagrams, there is usually an empty rectangle for the attributes box.

I was wondering if both are acceptable and which is preferred.

Thank you!

[damithc]

Not compulsory. OK to omit if empty. :-)

[Nikhilalalalala]

Thank you!