Can java make games for any OS? even mac ?

Question

I want to make a game and I'm not sure people with apple products will be able to play

Answer 1

once packaged the application runs everywhere that has jre

Answer 2

You can makes games for Windows, Linux, Mac, Browsers, Android, iOS by using LibGDX game library. LibGDX is a popular game library for Java.
My recommend you to read books to know how to use libGDX: https://www.packtpub.com/all?search=libgdx