Yay, someone who also realizes that concurrency is somehow easier in assembly. Last time I heard that from anyone else was from Erik McClure.

It's sad it's taken this long for some things to be so simple in Java.

Also up-voted this, because it's good programming, something that comes around only every once and a while.

Thanks switch. I agree, I have no idea why everything in Java has to be so stupidly complex. It shouldn't take a month to learn how to make a safe concurrent program.

Does the design here seem to make sense to you? I haven't had anybody review this design yet, so I'm not entirely comfortable with it. Do you think the whole premise makes sense, where you let users return Status.RetryLater and send their Task to the back of a queue? I intended it as an easy way to allow blocking without occupying a thread, but I have a sneaking suspicion that there might be something wrong with it...concurrency is confusing after all...

I am not the one to ask about this. I simply don't know enough to verify that the way you are doing this is right.

Given, I did take a quick look at it and it seems like an ok way of going about it. The factory implementation and using queues does make sense but I think it is a rather old way of handling concurrency and I am unfamiliar of any newer ways of doing it.

From wikipedia, Java usually uses Shared Memory for communication between threads. So as long as you are handling the application with some form of locking (e.g., mutexes, semaphores, or monitors) to coordinate between threads it should work. Rosetta code some information on Java concurrency: http://rosettacode.org/wiki/Concurrent_computing#Java And with using a mutex: http://rosettacode.org/wiki/Mutex#Java

I'd say look at other implementations for concurrency in another language and do a comparison if you can. It sounds like you are doing some of it right.

You may get a better more thought out response from http://lobste.rs/ if you are a member there. If not ask on Hacker News to get an invite for it. They are always posting some fairly in-depth programming discussions and you might get more of a response there.

Also try reddit r/programming they can be harsh but helpful at times.

I am not much of a fan of java. I'm much more of a fan of whatever fits the job best but in most cases that is C/C++. It doesn't suffer from "enterprise everything with long ass names" like Java or C#. C has some decent threading/concurrency libraries just because when people do performance work on computers they often go for C because it is very close to bare-metal.