Originally Posted by keepStriving
Find a matching version of the book or software.
Perhaps design your own Rock to substitute.
I do not know anything about gridworld either but that does not mean you can't find help here.
You never say what is wrong with the code. You say there is no rock, but to people unfamiliar with gridworld, what is a rock? Is it a class? Or a variable? Perhaps a package?
Is there a compiler error or runtime error? Always post the full text of errors with your question and code.
What we need to be able to help you is a description of the problem, what works and what does not. What did you expect the code to do as you have written it, and what does it actually do?
If you can not explain better what is wrong, then my final suggestion would be to not play with broken toys just yet, and find an educational tool without internal errors