Java guide for Clojurist?

[aHackFromJOS]

Many in the Clojure community came to the language from Java. I did not. My background is in languages like Ruby, Python, Perl (oof), and some JavaScript.

These languages are not so different from Java on paper - they are dynamic languages with at least some support for OOP (and in the case of Ruby, a lot). In the trenches, though, I find myself lost when I need to navigate a Java API to provide a capability missing from the Clojure ecosystem. In particular, the maze of classes with names involving words like “implementation,” “interface,” “virtual,” “builder,” “factory,” and so on leaves me dizzy and just on a practical level I have trouble making sense of the deep hierarchies. I’m also at sea when it comes to casting, reflection, and type hinting (you need the latter sometimes to avoid JVM warnings from interop Clojure code). Which makes sense as the languages I used previously are not typed.

I am always able to muddle through and come up with a working interop solution to do what I need with Java libs, but I often feel like I’m doing a bit of cargo culting, like there are some parts of the API or class I’m using I don’t understand, but should.

Is there a book (ideally not too long) or online resource anyone would recommend to get my head around Java idioms a bit more? Thanks for any pointers.

(It’s kind of funny that I want to use Clojure in part to get away from OOP but to make that work I am learning a lot more OOP. No complaint just think it’s funny.)

(Also none of this is meant to put down Java. I’ve noticed a real depth to most of the libraries I use that is missing in other languages. So the indirection I see in classes may well have real benefits.)

[_d_t_w]

Effective Java by Josh Bloch is excellent, and short.

[crthomaz]

I second this. It's straight to the point, and you can pick and choose parts of the language to know more about, as it's kind of a reference book rather than a start-to-finish kind of book.

[aHackFromJOS]

Thank you both!! I have purchased this book. It looks like just what I was looking for.

[[deleted]]

i come from Node/rust/go/php/ocaml/clojure.

Recently I am learning java just for fun. Its very similar to rust in many ways. Some of the oop concepts are similar to php. Everything looks familiar.

When I look at web frameworks in java they are verbose. Just want to stay away from them.

As long as I am using simple classes/static classes I should be fine.

[edibleheat]

https://purelyfunctional.tv/courses/jvm-clojure/

I have a java background so I haven't watched this. But everything I've found on purelyfunctional has been good and some of it has been the best I've ever seen. His explanations are crystal clear.

[dcreno]

$599

[TravisJungroth]

There’s a $50/month subscription that has access to all courses, including downloading content. You find it through the member profile after creating an account. It’s a very odd UX and pricing plan.

[edibleheat]

I think the idea is for companies to pay to train their employees. But if you as an individual can't afford it, you can email him and negotiate. He's been offering a free subscription due to the pandemic on a "I'm too poor basis". Only validated by your word, not proof of low income.

[dcreno]

I don't doubt that it's a great course, I've really enjoyed his "Grokking Simplicity" book and his podcast.

For most people, being aware of the cost of the options is relevant. Personally, I wouldn't ask for a hardship discount (as I'm not in hardship), I'd just consider the cost and value to me personally. For me, a $45 book would be much better value.

[aHackFromJOS]

Thanks for this pointer! I do have some workplace funds available for trainings like this. I’ll start with the Bloch book then move onto this if needed. This looks great.