Author here. I started using Lisp for AI in the early 1980s, had a Lisp Machine, wrote two AI Lisp books for Springer-Verlag back then, etc. I thought that Java 1.0 was an interesting language, and Peter Norvig, who did a tech review of an early edition of this book once said something to me roughly like 'Java is half as good as Lisp for AI, but that is probably good enough' (from an email probably 12 years ago, but that is close to what he said).
Clojure, Python, Common Lisp, are other candidate languages for AI.
Clojure seems like a pretty natural choice, especially if you are planning to use a lot of third party libraries written in Java (though even CL might be useful, if you use ABCL). I suppose the real question here is, "Why Java?" Are there technical considerations, or is it about the syntax being more familiar to potential readers, or is there some other consideration here?
Clojure is a natural choice. One reason this book uses Java is that I wrote the first edition in 1998, this being the fourth edition. I still like Java simply because I use Clojure and JRuby a lot and Java interop is easy.
I love to write, and if I could get a world class Clojure coder (perhaps someone like Alex Ott, or someone with similar skills) to co-write, it would be fun to start over.
Why did you choose Java over Python (imo the only two practical alternatives for a textbook since you want to target the biggest possible audience)? Are the Java AI/ML libraries better or easier to use than Python's?
Clojure, Python, Common Lisp, are other candidate languages for AI.