[jerf]

It means that when it comes to writing code to deal with a query language, which involves having an AST and manipulating it every which way, Java gets creamed by many other languages. Both the Lisp series of languages (which Clojure is in) and the ML series of languages have wildly better stories for dealing with AST manipulation, as in, better enough than Java that it's worth learning those languages just for that, if that's the task you have.

Whether or not Java is a "bad" choice is a definition issue, that it is handily beaten by many other languages is pretty concrete.

I'm not saying this as a Clojure partisan, or a Java-hater, or anything like that. I'm saying it as one who has used enough of the relevant languages to know it's not even close.

For something more concrete, I'm more on the ML side, so work through https://en.wikibooks.org/wiki/Write_Yourself_a_Scheme_in_48_... and you'll see what I mean, even if you just do the first couple of chapters. For all that Haskell may be weird in some ways, consider what it means for a tutorial of a language to be talking about parsing in the second section. You'd never get that with Java.