Opinionated (and premature) wrap-up of Devoxx Belgium 2024 - JVM Weekly vol. 102

Today, we're going to have a more relaxed travel and conference edition.

Oct 11, 2024

I had the chance to attend the Belgian Devoxx with my new talk. I’ll come back to that topic later (because of course, I want to share the recording with you), but at the same time, I want to use this edition to tell you why Devoxx is such a great event and why you should definitely visit - along with a few thoughts about the event itself and the state of our industry 😃

First, I'll mention that this was my first Devoxx outside of Krakow and also my first time in Belgium, so I'll start with the very touristy aspect of it—Antwerp is beautiful, especially after the rain, and just walking around after I arrived brought me a lot of joy. I absolutely need to come back with my wife and daughter for at least an extended long weekend, especially since it's only an hour away from f*cking Bruges. I heard it's like a f*cking fairytale or something.

"In Bruges"... top three of my favorite movies. Maybe I’ll share the other two one time.

tself, just like the Krakow/Prague Geecon, takes place in a cinema—Kinopolis—and I must admit that while during the first workshop days, when there weren’t many participants yet, you could easily move between exhibitor booths, during the actual conference days, things got quite... cozy. Take a look at the photo below.

What’s particularly great about Devoxx is that everyone is here! Practically every major "infrastructure" company has a booth. You can talk to people from Oracle, RedHat, Azul, BellSoft, Google, Microsoft, and smaller players like Testcontainers, Vaadin, and many more. If you're really into behind-the-scenes details, you can learn a lot.

The conference also helps you better understand the Zeitgeist of the times we live in. At Devoxx, about one-third (maybe someone will attempt a more accurate statistic) of the talks were broadly focused on AI. I can’t blame anyone for it (after all, my talk was also JVM in the Age of AI), but this was especially visible in the lineups of the big players. Take a look at what talks Microsoft offered us:

Out of six, five were about AI. The ratio wasn't much different from other companies. Overall, AI was the main topic at Devoxx, and I’m wondering if this is just for this year and we’re currently at a peak or if the trend will continue. I suspect that 2025 will start showing us where things are headed, but I don’t expect any brakes to be applied.

However, it's Testcontainers that win the prize for the most subtle sneaking of AI into their brand.

Devoxx is also the perfect place to gather some awesome industry swag. And when I say I’ve always wanted RedHat’s iconic red hat, I’m being completely sincere. So, I’m beyond grateful to have received one—not once, but twice! First, from the fantastic team at the RedHat booth, and then from Krystian Leszczewski , who generously gave me his after I lamented I’d lost mine at the Speakers Dinner (because, yes, that actually happened...).

And they say people don’t have empathy anymore. The world is a better place than we all think.

It definitely fits the rest of my outfit.

Lego Duke from Azul also stole my heart—just last weekend, my wife lifted the embargo on Legos for our three-year-old daughter, so one of her first sets (after the horse stable) will be this handsome guy.

In general, a lesson for the future - I need to take more pictures. I really want to show you more booths, but I just don’t have enough material. I promise I’ll do better next time!

Now, here are a few (literally just a few, as there were too many talks at Devoxx to describe even a large portion) that I particularly enjoyed, because I had the chance to watch a bit. One of the advantages of Devoxx is that talks are available almost immediately after they are given, usually within 24 hours:

Pushing Java to the Limits: Processing a Billion Rows in under 2 Seconds

Last January, Gunnar Morling asked a seemingly simple question: how fast can you parse a file with a billion rows of weather data using Java? What began as a casual challenge turned into a deep dive into the worlds of concurrency, memory-mapped files, SWAR techniques, bit manipulation, branchless code, mechanical sympathy, Graal native compilation, and of course, a journey to the dark side with sun.misc.Unsafe.

Thomas Wuerthinger and Roy van Rijn took us on a three-hour journey through every trick and optimization that helped them reduce processing time from over 4 minutes to less than 2 seconds. And I must admit, the fact that I sat through such a long session was proof of how engaging the presentation was. Though the "cinema experience" certainly helped—it was a bit like MCU movies: they hold your attention in the theater, but if I try to focus on a Marvel movie at home, I always end up grabbing my phone. Such long formats probably work best as group experiences.

But overall, it was an amazing presentation.

Looking at Music, an experiment with Kotlin, JavaFX, MIDI, and Virtual Threads

So what happens when you combine music, MIDI, Raspberry Pi, and JavaFX? No, this isn't the start of a bad joke—this was a session at Devoxx, and you know what? It worked. MIDI controlling a Raspberry Pi, JavaFX turning the screen into a music visualizer, and your piano keys lighting up LEDs like you’re hosting a rave in your living room.

But the best part? It wasn’t just theory or boring code on slides. No, no. In this unique session, Frank Delporte talked code, and his 14-year-old son Vik Delporte played piano live, generating thousands of Virtual Threads. A mind-blowing combination.

And during the Q&A? Two pianists on one keyboard! Only at Devoxx have I seen something that felt like a cross between a coding bootcamp and a classical music concert.

Empathic Mentoring for Developers - Why Should You Care, and How?

This was a more serious presentation, tackling tougher topics. It discussed how mentoring in IT can change lives, both for the mentor and the mentee. Derviş Mansuroğlu showed that mentoring isn’t just about helping someone find a job; it’s also about confronting your own biases and demons—like a personal horror story.

A great presentation, definitely worth watching.

Top REST API Design Pitfalls

In a world where everyone is obsessed with language models and AI, it’s strangely refreshing to get a session on something as classic as REST API design. Seriously, how retro is that? It’s like a trip down memory lane, but instead of reminiscing about floppy disks and modems, we’re analyzing API design nightmares - domain leaks, privacy disasters, performance issues, and the curse of overloaded PUTs. Victor Rentea lovingly gathered these horror stories from over 150 companies and delivered them with his top-class style!

Talking about retro technologies...

Squeezing Mushrooms into Bytes : Mario's NES Memory Magic

So imagine this: you’re coding, right? But it’s not today’s “just spin up an instance in the cloud.” No, no, we’re talking about the good old days, when your processor had the power of a potato, your RAM barely remembered what you told it, and memory? Good luck with that. But, oh, the video game industry—those maniacs didn’t just manage, they thrived!

In his presentation, Clément de Tastes dove into this wild world, where developers did the impossible, like cramming Super Mario Bros. into 40KB on an NES cartridge, or performing magic with the ‘Fast Inverse Square Root’ function in Quake III. As a fan of retro games, I was more excited about this than if I were a kid opening a fresh Game Boy in ’89 (and I was born in 1990, which just adds to the drama).

Also, it was a pleasure to be at the last Devoxx. If Nintendo finds out what was on the slides, they’ll shut the whole event down 😞

I also had the chance to speak at Devoxx, and it was a fantastic experience. Although it caused me some stress (especially since my talk was mentioned during the Keynote by Stephan Janssen himself ), and the material I chose meant that I had to deliver the entire presentation in one breath (152 slides in 50 minutes—and I still had a minute to spare!), I'm super happy I got to be part of the event, and I’ve got zero regrets.

If it's too fast - pro tip: play at 0.75x speed

Here are the slides, and additionally, a few sessions that, if you like the material, will help you dive deeper into what I discussed:

Another Protip: Being a speaker is great, especially because of the speaker dinners - and not only for the food but mainly for the company.

Now for the solution to the riddle—why “premature” in the title? Because I had to leave on Thursday, which means I missed a few really cool sessions, but they can easily be caught up on—after all (as I’ve mentioned more than once), Devoxx lets you watch them online. So even though I can't (yet!) comment on their quality, I already know I’ll catch up on

For example, today’s edition was written on the bus and at the airport in Eindhoven.

And next week, a regular edition... because I’ve got enough material for at least two 😉