Maven cache .m2 is under $HOME/'?' folder

I installed clojure through nix-shell -p clojure. clj successfully started the repl after downloaded some poms from maven. Then I found there is a folder named ‘?’ created under my $HOME. The maven cache .m2 is under this ‘?’ folder. I tried leiningen, it is the same. I suppose it should be a Java related issue rather than Clojure. But I’m not so familiar with Java to verify it. Is it normal to have .m2 under $HOME/’?’ ?