"Top-level nested class" is an old term for a static nested class. Calling this "top-level" was a bad idea in the first place, needlessly confusing (how can something be both nested and top-level?), and when Sun released the Java Language Specification 2nd edition in 2000 (I think), they removed this horrible bit of terminology. (Thank you, Sun.) Unfortunately many books still exist which use the term, either because they're old, or the author(s) didn't realize the olde term had been removed from the language. So, any time you see the term "top-level nested class", just pretend they said "static nested class" or "static member class" instead. And please, please don't continue to spread the term "top-level nested class" as it's been dead for some time now.