concept of variable-free programming

Can anyone clearly explain the "concept of variable-free programming",
in Object Oriented Programming with a sample code.

I found this in a java assignment, it says that

Your program must adhere to all the standard Java programming style guidelines including code readability, logical clarity, scoping rules, proper use of class and instance variables, encapsulation, naming conventions for classes, methods and variables and

"concept of variable-free programming".

Thank you very much

Cross-posting between forums is guaranteed to annoy people - your question has been answered in the other forum, so I suggest you modify your post here to indicate that.

There does not now, nor will there ever exist, a programming language in which it is the least bit hard to write bad programs...
L. Flon