How to learn concurrency?

That's a huge topic but I would say implement a hobby project and learn by doing. Pick something you're interested in and start writing code to exercise the theoretical concepts.

A small piece of advice is to make sure you're motivated before diving in. Debugging a race condition, just as an example, can be quite involved and consume a lot of your time and energy to even reproduce.

Brilliant.org?

https://deadlockempire.github.io/

https://thecomputersciencebook.com/book/concurrent-programmi...

Everything I know is from desperately trying to parallelize my TIS-100 solutions.

Start by learning how to use a search engine?

Java Concurrency in Practice[1] has always been recommended by my colleagues. I'm about halfway through it and I think it makes the concepts pretty clear. Even if you move away from Java one day, I think the investment is not lost at all. Then you could ask your favorite LLM to create concurrency exercises once in a while to practice.

[1]: ISBN 978-0321349606

https://docs.oracle.com/en/java/javase/25/core/concurrency.h...

Read a book about OS's I guess. This should be good, an update of an earlier good book: https://www.os-book.com/OS10/

There was a Java-specific edition: https://www.os-book.com/OS8/os8j/index.html

Something I've built for myself (in Go) that has been extremely useful is a lib to read a CSV that delegates to n concurrent workers.

Maybe that is a good side project.

1) Foundations of Multithreaded, Parallel, and Distributed Programming by Gregory Andrews - https://www2.cs.arizona.edu/~greg/mpdbook/ This will give you a solid foundation in all aspects of concurrency.

2) The Art of Multiprocessor Programming by Herlihy, Shavit et al. - https://shop.elsevier.com/books/the-art-of-multiprocessor-pr... The classic must-study book.

Both the above are not language specific but do have examples in Java.

Once you've gone through the learning resources others shared, LeetCode has a dedicated concurrency section for hands-on practice: https://leetcode.com/problemset/concurrency/

(I actually authored a few of those problems - they cover the classic scenarios like producer-consumer, dining philosophers, etc.)

Docs of java.util.concurrent would be my suggestion. And go straight into the wild and try to build a system that solves the billion rows challenge. You might want to truncate the input and start with a million row challenge first.

The cool stuff in concurrency is not having to deal with it imoand recognizing when its not essential. Also I hope you mean concurrency not parallelism. The second one is a bit more manageable.

If you don’t mind learning another language. I have found Learn Concurrent Programming with Go by James Cutajar to be a very practical book. It includes memory sharing and message passing approaches with plenty of examples. It also explains concepts like mutual exclusion, deadlock-free and starvation-free properties and others. For Java, you can try The Art of Multiprocessor Programming Second Edition. It includes examples in Java but it is more theoretical and it includes a lot of proofs, specially the first half. The second half is more approachable.

Do you know, deep down, what a thread is? What it actually is?

If not, I suggest reading this blog post: https://prettygoodblog.com/p/what-threads-are-part-2

(disclaimer: I wrote this)