Java for sure has good tools for concurrency, and you listed some of the very interesting choices! However the flexible nature of Java concurrency also has the

Java for sure has good tools for concurrency, and you listed some of the very interesting choices! However the flexible nature of Java concurrency also has the drawback that you might need to integrate different libraries that utilize different concurrency solutions (blocking threads, actors, non-blocking eventloops) with each other. This can end up in a lot more effort than if you try to use multiple libraries in an ecosystem with a single opinionated concurrency solution (like Go for blocking IO or node for pure nonblocking IO). The weakest ecosystem regarding this is imho C++, where most concurrency/IO solutions only work well if you don't try to also use other solutions in parallel (e.g. QT plus glib plus boost asio plus libuv...).