Opinionated wrap-up of 2025's JavaZone - JVM Weekly vol. 145
This time, a photo report from the land of the Vikings… and the Romans?
Hi and welcome to another edition of JVM Weekly! Last week I had the great pleasure of visiting Oslo for the JavaZone conference - not just as an attendee, but also as one of the speakers. So today’s issue will have a slightly different shape - treat it as my subjective photo-report and a collection of impressions from one of the most extraordinary IT events I’ve taken part in. And there was a lot going on.
Let’s start at the very beginning, because even the speakers’ welcome surprised me pleasantly. Most conferences hand out swag bags with gadgets, T-shirts or other little presents. This time it was different. The welcome gift for us speakers was the news that a donation had been made on our behalf to support the fight against endometriosis. That’s an extremely thoughtful and commendable gesture, especially given that this is a condition that genuinely and painfully affects many women’s lives.
Huge credit to the organizers for that social sensitivity. I really appreciated it.
I’d heard JavaZone was produced with flair, but what I found on site exceeded my wildest expectations. This year’s theme was Ancient Rome, which the organizers used with incredible creativity. In addition to the omnipresent Roman-style logo, a Gregorian choir appeared on the main stage:
and Asterix and Obelix strolled through the corridors to the mentioned stage.
But the unofficial prize for best use of the theme goes to the company JetBrains for their adorable Kodee dressed as Roman Emperor. Pure cuteness!
Speaking of food… well, it was good. Really good. Almost too good, because I don’t think anyone expected conference catering at that level.
It was varied, tasty, and available in huge quantities... I got back from conference ~1kg heavier.
Evenings were for concerts. And we’re not talking about nerdy bands like you sometimes see at Devoxx UK (The LineBreakers - I love you with all the heart ❤️). The real bombshell, though, was the duo behind the hit that had the world humming a few years back - yes, Ylvis (the What Does The Fox Say? guys) performed. Seeing them live at a tech conference was a bit surreal experience.
Interestingly, while all that JavaZone has a surprisingly local character. At the largest conferences, like Devoxx, we’re used to global tech giants dominating the show floor. Here, most booths belonged to Norwegian companies, featuring Norwegian job postings and offers. Sure, there were big names like Red Hat and Google, but their booths were surprisingly modest compared to the local players. That gave the whole event a unique, more intimate vibe which definitely worked in its favor.
What wasn’t in short supply, though, was games! Because of the event’s entertaining character, almost every company seemed to try to attract visitors with some interactive game. You could play classic Frogger, tackle Sokoban, and many other games. For me, the highlight was the booth where you could shoot ducks with an original NES lightgun at CGI stand.
You could also play chess in the expo venue. With human..
.... and with robot 😁
Apart that, there was an option to play with Arduino (with all the instruction in Norwegian, which was... kinda fun.
You could also ride a bull... I learned I'm not very good at it 🙈
Or even Mario Kart: World on Switch 2.0.
The main event of the event was the poker night - during a day, you could collect Duke Dosh...
... which could be used during the evening party.
But the absolute hit - and, from my perspective, the most valuable entertainment - was a game by Telenor that teaches CSS with Roman legionaries as the main characters. I have to admit: my old nemesis, styling with flexbox, suddenly lost its bite.
After a short interactive intro I was able to arrange objects on a page quite quickly and smoothly. Not because I suddenly became an expert, but because the game was brilliantly designed. I’m pretty sure I’ll never write float: left again.
My conclusion? JavaZone is the ultimate proof that no - even the best - remote conference can give even a fraction of the experience you get in person. It wasn’t just a conference - it was one fantastically staged show.
Okay, but a conference is first and foremost about knowledge and talks. So at the end I have a few sessions I recommend you pay special attention to.
30 Years of Java - How we got here?
Simon Ritter talk, 30 Years of Java – How we got here?, is a comprehensive overview of the history and evolution of the Java programming language.
Ritter, drawing on his experience since 1996 at Sun Microsystems, presents Java’s origins as Project Green at Sun in 1991, initially named Oak, intended for smart devices, and its market debut in 1995 under the slogan “Write once, run anywhere.”
The talk also covers Java’s version evolution, naming issues, and milestone moments like the Sun vs. Microsoft dispute, Java’s open-sourcing as OpenJDK, and Sun’s acquisition by Oracle. Ritter wraps up by showing Java’s diverse applications over the years - from SIM cards to Blu-ray players - and the role of the Java community in its ongoing development.
From Ballots to Code: Exploring Election Security
Hallvard Nygård talk From Ballots to Code: Exploring Election Security presents the results of his extracurricular research into the security of Norwegian elections, which he began in 2019. He emphasizes the critical importance of trust and anonymity in democratic elections, requiring transparency, auditability, and resistance to tampering. Analyzing the Norwegian system - which relies solely on physical paper ballots and combines manual and electronic counting - he identified serious physical security weaknesses, such as how easy it is to duplicate official election seals and insufficient protection of ballot boxes transported in plastic containers, enabling vote manipulation. In his talk, he is showing that digital voting is more complex topic than it seems.
Nygård urges citizens to take an active role in observing elections, asking questions and documenting the process, which he believes will help improve security and transparency.
The Programming-Lang of the Future
The Programming-Lang of the Future discusses Gren, a new programming language based on Elm. Gren’s creator, Robin Heggelund Hansen, explains the motivations behind it, pointing to shortcomings in the predictability and transparency of modern languages like JavaScript or Java. Robin argues that despite their evolution, these languages still force programmers to read implementations to understand behavior, which doesn’t scale in large projects. Gren aims to solve these problems by offering strong language guarantees - no mutation, no exceptions, and no uncontrolled side effects - and providing first-class support for building backend applications and command-line tools, which Elm lacked.
Nice nerdy stuff.
Building AI Agents with Spring & MCP
Of course there were agents - after all, it’s 2025.
Building AI Agents with Spring & MCP by Josh Long and James Ward presents Spring AI and its use for building AI agents. The speakers show how to build, for example, an assistant for dog adoption by combining Spring AI with various technologies. They explain the use of vector databases (like PostgreSQL with pg_vector), integration with AI models (e.g., Amazon Bedrock, Cohere) and Retrieval-Augmented Generation (RAG) techniques. They also covered using Spring Boot Actuator to monitor token usage, introducing tools that allow agents to interact with business logic, and demonstrating how to extract those tools to external MCP servers for scalability. And the presenters are genuinely funny and have great chemistry, which is always a plus 😁
I just regret not being able to attend Mary Grygleski talk on the same topic at the same time - shame on you, JavaZone! Fortunately the recording is already available, so I’ll catch up in my spare time.
JavaZone also had a strong Polish presence 🇵🇱. Besides my talk about the Nintendo Entertainment System and kNES - Kotlin based emulator, I attended a great talk by Grzegorz Piwowarek about what Java developers can learn from Go - surprisingly solid fundamentals and very practical takeaways.
I also caught Marcin Moskala session on Kotlin - Kotlin variance modifiers and Covariant Nothing Object pattern - and, as always, I don’t regret it. Marcin is the owner of kt.academy and, in my opinion, one of the best Kotlin trainers not only in Poland but in the broader community, so if you want to learn more about the language his materials are always a must-have.
Small friendly shout-out: Marcin is preparing a new edition of his coroutine course and I think you should know about it - I’m not saying that just because I came back from the conference with his signed book, but cause the course looks unique, has games, nice examples and even interviews with people like Roman Elizarov (leader of Kotlin’s coroutine work and the “father” of coroutines), so the material will be top notch.
What do I regret? Mostly that I don’t know Norwegian, because on Thursday there was a session about writing GameBoy editor in Rust (that I would have loved to listen to). I’m really hoping that next year AI will be advanced enough to simultaneously translate sessions for us live. That would be so much fun.
Not saying I Dare You, JavaZone, I will definitely come to check next year 😁. It was fun!
PS: Today’s issue is shorter because I’m simultaneously finishing a long, detailed report on what’s new in JDK 25 - coming very soon. This time I intend to dig a little deeper than usual; I hope you’ll like it.
PS2: Over the weekend I decided to spend some time in Bergen with my wife, daughter and cousin. We drove from Bergen to Oslo while listening to Neil Gaiman’s Norse Mythology - an unforgettable experience. All in all, I have to admit that although it wasn’t my first time in Norway, the country is simply stunning.
If you enjoy driving even a little and have the chance to rent a car, do it - it’s stunning.
PS3: I already started to work on the followup to my NES talk. Stay tuned, it will be soooo fun for both sides of the stage!
PS4: See you on Confitura Conference next week in Warsaw! You can still buy tickets 😊