Author: Marit van Dijk

Marit van Dijk - Software Developer, Java Champion, Senior Developer Advocate at JetBrains. She is an international keynote speaker and author.

JCrete; the hottest unconference on the planet!

Last month I had the honor of attending JCrete; “the hottest unconference on the planet!” I had heard many great things, and it certainly lived up to its reputation.

Unconference

JCrete is an unconference; the attendees create the program. Every day starts with a “marketplace”, where anyone can suggest a session. At JCrete, attendees then vote on the proposals and the most popular ones are scheduled in the available time slots and spaces. A session can be a presentation, but more often are discussions where people can share their thoughts and experience, and help others. It is much more interactive than a regular conference. Think of it as one big hallway track!

Marketplace at JCrete (Picture by Sven Woltmann)

Sessions

There were lots of interesting sessions on Java, AI, and other topics. You can find notes on some of the sessions here, but you really have to experience it for yourself.

Java: Virtual Threads and Scoped Values

Some of my favorite sessions were the ones by José Paumard on Virtual Threads and Scoped Values. In this smaller setting, there was room for lots of discussions and sharing. At some point, I even managed to give José some tips for IntelliJ IDEA which he immediately applied. Did you know you can use the live templates iop and ior for IO.println() and IO.readln()?

Live templates for IO.println() and IO.readln()

Impromptu presentation

Several people in the session asked for more tips, and there happened to be some time left at the end of the session. The only available laptop was José’s machine: a Windows machine with a french keyboard! This was certainly an interesting challenge in doing my demo. With the help of José , I managed to show a few tips…

Marit van Dijk behind a lecturn at the Orthodox Academy of Crete. The screen behind her is showing IntelliJ IDEA.
Impromptu presentation (Picture by Anita Przybył)

IntelliJ IDEA Tips & Tricks

This prompted me to suggest a session on IntelliJ IDEA Tips & Tricks for the next day. Here I managed to show all attendees something about IntelliJ IDEA they didn’t know yet, even my colleague Anton Arhipov (who has been using IntelliJ IDEA for much longer than I have).

When I told Pasha Finkelshteyn about this later, he asked me what it was because surely it would be something he didn’t know either. It turned out to be something he had been looking for recently!

The tip in question? You might know that you can use F2 to navigate to the next problem in a file (or Shift +F2 to go to the previous problem). By default, this cycles through problems by severity; errors first, warnings next, etc. To change this, hover over the Inspection Widget at the top right of the editor, click More (the three dots), click ‘Next Error’ Action (F2) Goes Through and select All Problems

IntelliJ IDEA – Change the order for Next Error action via the Inspection Widget

Alternatively, you can use Search Everywhere (press Shift twice) to look for the setting The ‘Next Error’ action goes through in Settings | Editor | Code Editing and select All Problems there.

IntelliJ IDEA – Change the order for Next Error action in Settings | Editor | Code Editing

Code reading

Eleftherios Chrysochoidis suggest a session on code reading; a topic dear to my heart. Lots of interesting things were shared by the people in that session including Thaddeus Müller-Sarnowski, Ina Bumstein, Jakub Łątkiewicz, Lenny Primak, Marharyta Nedzelska. Of course I also shared links to some of my materials on this topic.

Other activities

JCrete is held on the beautiful island of Crete, which means lots of sun and the opportunity to visit lots of beaches. Fortunately, I also had the opportunity to join a trip to the botanical gardens with Gunnar Morling and his family; the gardens were beautiful, and shade and breeze were very welcome.

At the botanical garden with Michal Niczyporuk, Gunnar Morling and his family.

We also has the opportunity to visit an olive grove. Unfortunately, I was not able to buy any olive oil as I had only hand luggage.

We often ended up at Mylos near the beach in the (late) afternoon.

Michael Minella, Arno Koehler, Estelle Landry, Michal Niczyporuk, Ana-Maria Mihalceanu, myself and Andres Almiray at Mylos.
Ana-Maria Mihalceanu and I at Mylos.

And in the evening there was time to enjoy delicious Greek food.

Me, Ana-Maria Mihalceanu, Grzegorz Piwowarek, Paulina Słąba, Andrzej Grzesik, Ewa Karaszkiewicz, Michal Niczyporuk, Anita Przybył and Piotr Przybył at dinner.

Thanks

After an amazing week, it was time to say goodbye. But not before getting the mandatory selfie with Heinz.

Selfie with Heinz Kabutz

Many thanks to Heinz Kabutz, the disorganisers Ixchel Ruiz, Andres Almiray, Dmytro Vyazelenko and others for an unforgettable week! I hope to be back in the future…

Group picture

Devoxx PL: Talks, booth, and wonderful people.

The last conference of the “Spring” 2026 season for me was Devoxx Poland. This was my third time speaking at this conference, and my second trip to Kraków this year.

This year I again had the honor of delivering two talks: Getting more out of Maven (without Andres Almiray this time) and Reading Code.

Polish JUG Meetup

The evening before the conference I went to a Polish JUG meetup, to meet up with friends Adrian Nowak, Ida and others. Adrian gave me a GeeCON shirt and sticker. It was also nice to see ex-colleague Pasha Finkelstein, who was speaking at the meetup.

Day 1

Since I was giving two talks, I spent some time preparing for them. Especially as I would be giving the Maven talk by myself this time, as Andres unfortunately was not able to make it. And also it had been a while since I last gave my Reading Code talk.

During the day, I did go meet my colleagues at the booth; conferences are always a good place to see and meet colleagues. JetBrains has offices all over Europe (including Poland) and several other countries.

JetBrains booth with Jarek Dąbrowski, Marcin Aman, Emilia Obiała, Katerina Trendafilova, Piotr Tomiak and myself (Picture by Nel Gwiazdowska)

At the end of the day, I went to see an new talk From compose.yaml to Testcontainers: testing Kibana with one line of Java by Piotr Przybył.

After that, it was time for the meet and greet; a great opportunity to talk to other speakers and attendees.

Day 2

On day 2, it was time for the first one of my talks: Getting more out of Maven in the main hall.

Speaking in the main hall (Pictures by Nel Gwiazdowska)

Based on the positive feedback I received, I would say the the talk went very well as a solo talk.

And even though Andres was not there in person, here was there in spirit.

A picture of Andres Almiray featuring in the slides.

@andresalmiray.com 404 😕

— Johan Hutting (@johanhutting.bsky.social) 2026-06-18T07:02:09.038Z

Later in the morning it was time for Reading Code. When I first submitted this talk to Devoxx Poland two years ago, a friend on the Program Committee sent me a nice message about how much they liked the abstract. Unfortunately, it was not selected that time (but another talk was). So it was nice to be able to finally deliver this talk here.

Before the talk (Picture by Nel Gwiazdowska)

Thanks to my colleague Ernest Mołczan for coming to my talk.

Ernest Mołczan sitting in the front row. Marit van Dijk is speaking in the background. (Picture by Nel Gwiazdowska)

With both of my talks done, I had time to see some talks in the afternoon.

First, it was time to see Refactoring to Modernize Java Applications by Venkat Subramaniam. If you have ever seen Venkat speak, you know it is always well worth your time.

Piotr Przybył, Venkat Subramaniam and myself (Picture by Piotr Przybył)

Next, I went to see another talk by Piotr Prybył, SIMD for Java: how Elasticsearch already benefits from the Panama Vector API. During his talk he reused a demo from our talk Learning modern Java the playful way, but with way more in depth information about Vector API and how Elastic uses it.

With Anita Przybył at Piotr’s talk (Picture by Dimitris Doutsiopoulos)

After that I joined the talk IntelliJ Super Productivity in 45 Minutes by Heinz Kabutz. It is always interesting to see how other people use IntelliJ IDEA, what features they prefer and how they customize it.

Piotr Przybył, Heinz Kabutz and myself (Picture by Piotr Przybył)

Speaker dinner

In the evening it was time for the speaker dinner. It was a nice walk to get there, in the company of Anita Przybył and Katarzyna Leszczyńska-Bohdan. The dinner itself was great, with some delicious pierogi and other food. And of course great company.

With Anita Przybył at the speaker dinner (Picture by Dimitris Doutsiopoulos)

Day 3

On day 3 I attended a talk by Simone de Gijt. I love her talks; the topics are very interesting and her stage presence is great. Imagine my surprise when she mentioned me in her talk!

At the end of the conference I also managed to catch a talk about Dark Patterns by Sergès Goma. We had been at the same conference before, but had not yet properly met, so we finally got to fix that.

After the talks, a few of us had some conversations in the hallway.

Sergès Goma, Venkat Subramaniam, Marit van Dijk, Simon Maple, Balkrishna Rawool and Simone de Gijt.

In the end, being part of the community and meeting people in real life are the highlights of any conference.

Gerrit Grunwald and Marit van Dijk at Devoxx Poland (Picture by Dimitris Doutsiopoulos)
Marit van Dijk, Abdel Sghiouar and Dimitris Doutsiopoulos at Devoxx Poland
Marit van Dijk and Piotr Przybył at Devoxx Poland (Picture by Nel Gwiazdowska)
Marit van Dijk and Dimitris Doutsiopoulos at Devoxx Poland (Picture by Nel Gwiazdowska)
Jarek Dąbrowski and Marit van Dijk at the JetBrains booth at Devoxx Poland (Picture by Nel Gwiazdowska)
People at Devoxx Poland

Going home

After the conference, Simone and I took the bus back to the airport. We spent some time in the lounge, running into other speakers like Abdel Sghiouar, Simon Maple and Simon Brown.

Overall, Devoxx Poland was a great conference to close out the “spring” season; I hope to be back next year!

JetBrains booth with Jarek Dąbrowski, Ernest Mołczan, Emilia Obiała, myself, Piotr Tomiak, Katerina Trendafilova and Marcin Aman (Picture by Dimitris Doutsiopoulos)

Pictures

You can find the official pictures by Dimitris Doutsiopoulos here:

Your Java AI Agent at Home – Ronald Dehuysser | IntelliJ IDEA Tech Talks

In the third episode of IntelliJ IDEA Tech Talks, I talk to Ronald Dehuysser – creator of JobRunr, about the ClawRunr project. Ronald shows us how to use ClawRunr as a personal AI assistant and shares stories of how he uses it himself.

Description

What if you had a personal assistant who could check your emails, schedule tasks, prepare a legal dossier, and send a thank-you note, all from your phone while you’re on a ski slope?

ClawRunr is an open-source Java-based personal assistant that combines AI with background job scheduling. You chat with it in natural language, it figures out what to do, and Spring AI and JobRunr handle the rest.

Ronald Dehuysser, the creator of JobRunr, walks us through setting up ClawRunr, from choosing your LLM provider and connecting MCP servers to scheduling recurring tasks using live demos. He also shares what he learned taking it from a vibe-coded idea to an extensible demo app: why solid architecture matters for agent-style development, and why handing off as much as possible to the AI beats coding everything yourself.

Chapters

  • 00:00:00 – Introduction
  • 00:00:32 – What is ClawRunr
  • 00:02:23 – Setting up ClawRunr
  • 00:07:33 – From vibe-coded idea to demo app
  • 00:18:34 – Live demo with email triage, court case and scheduling
  • 00:29:57 – Recurring tasks and scheduling with JobRunr
  • 00:34:01 – What building ClawRunr taught us about working with AI
  • 00:38:31 – Closing

Links

Other episodes

More Java conferences: jPrime & JSpring back to back

June started off with not one, but two Java conferences: jPrime in Sofia, Bulgaria, and JSpring in Utrecht, the Netherlands.

When travelling to jPrime from Amsterdam, I already ran into two fellow Dutch speakers Hinse ter Schuur and Willem Jan Glerum at Schiphol airport. We were all on the same flight.

LinkedIn post by Marit van Dijk with the text: "On my way to jPrime Already ran into other speakers Hinse ter Schuur and Willem Jan Glerum" and a picture of a suitcase and backpack with IntelliJ IDEA labels on them at Schiphol.
Travelling to jPrime

Arriving in Sofia

Upon arrival in Sofia, we met up with Piotr Przybył in the arrivals hall, as he had landed just before us. We then proceeded to arrivals to meet up with Ivan St. Ivanov, one of the jPrime organisers, who drove us to our hotel.

At the hotel, Piotr and I had some lunch before preparing for our talk (as it had been a few weeks since we last presented it at GeeCON).

jPrime speaker dinner

We then walked to the speaker dinner where we met up with Mitya, other organisers and several other speakers including François Martin, Johannes Bechberger, Arnaud Jean. Also present was my colleague Andrei Kogun, who was attending the conference. It is always nice to see him in person, as we work together a lot but he is located in a different country.

Speaking at jPrime

Our talk Learning modern Java the playful way was scheduled right after the opening. It was really nice to speak in the big room in front of about 800 people (probably our largest audience for this talk so far!).

Marit van Dijk and Piotr Przybył posing for a picture on stage at jPrime. Both are wearing a labcoat.
Marit and Piotr at jPrime
Marit van Dijk and Piotr Przybył speaking at jPrime; both are wearing a labcoat.
Speaking at jPrime
Dmitry Aleksandrov announcing Marit van Dijk and Piotr Przybył at jPrime.
Mitya announcing us at jPrime.

Our talk was well received. Thanks to everyone who came up afterwards to talk to us! Meeting people is one of my favorite parts of conferences.

Social media post by Thanos Stratikopoulos: "Great start in #jPrime2026, features a playful way of learning modern #Java by Piotr Przybyl and Marit van Dijk (with links to their Bluesky accounts)
Great start to jPrime

Unfortunately, we didn’t get to stay long and we had to head to the airport not long after our talk.

Social media post by Piotr Przybył with the text: "It was sadly a short visit, but the crowd at @jPrimeConf has been lovely as always! I hope you've learned something useful about modern Java and also had some fun with us 🥼🥼" including a picture of Piotr Przybył and Marit van Dijk both wearing labcoats in front of a packed room
Thank you jPrime

You can catch the recording of our talk here:

You can also find pictures for day 1 and day 2.

Thanks to the jPrime team for having us and taking such good care of speakers!

On to the next one!

From Sofia, I travelled back to the Netherlands, to speak at JSpring the next day. While I had planned to go to the speaker dinner that evening, it was too tempting to go straight home as I live close to the airport.

Speaking at JSpring

JSpring is one of my local conferences, organised by NLJUG. This was my third time speaking there, and I have attended several years prior to that. The lineup this year was stellar as always!

Since the conference was in a cinema, they had posters advertising the speakers. It was slightly intimidating to see my face up there, but also very nice…

Speaker posters for JSpring speakers: Sven Peters, Baruch Sadogursky, Marit van DIjk, Nicolai Parlog, Ana Maria Mihalceany, Elena van Engelen, Bruno Souza, Felienne Hermans, Lucia Conde-Moreno, Josh Long & James Ward, Piet van Dongen, Holly Cummins
Speaker posters at JSpring

The conference was opened (as always) by Brian Vermeer and Bert Jan Schrijver, followed by the opening keynote by Sven Peters.

Bert Jan Schrijver and Brian Vermeer half hiding behind a JSpring banner.
Bert Jan Schrijver and Brian Vermeer at JSpring

This year, I really enjoyed the keynote by Felienne Hermans:

The following keynote by Baruch Sadogursky was also very nice.

My session Be more productive with IntelliJ IDEA was in the afternoon, so I had plenty of time to prepare. Even though the outline of this session is always similar, I like to include the latest features like command completion and upcoming features like logpoints (which is included in IntelliJ IDEA 2026.2). 

You can watch the session here:

You can find the full playlist for JSpring 2026 on YouTube.

As always, the best part of the conference was meeting people; both the other speakers and the people from the Duch Java community.

Marit van Dijk, Marianne Hoornenborg, Felienne Hermans and Ana-Maria Mihalceanu at JSpring.
With Marianne Hoornenborg, Felienne Hermans and Ana-Maria Mihalceanu at JSpring.
Marit van Dijk, Daniel Garnier-Moiroux and James Ward at JSpring.
With Daniel Garnier-Moiroux and James Ward at JSpring.

Thanks again NLJUG for organising and I hope to be back for many years to come!

What’s New in IntelliJ IDEA 2026.2

In this video, Marco Behler, Anton Arhipov, Siva Prasad Reddy K and I show you what’s new in the IntelliJ IDEA 2026.2 release.

Chapters

Links

Manage Skills Like Dependencies – James Ward | IntelliJ IDEA Tech Talks

In the second episode of IntelliJ IDEA Tech Talks, I talk to James Ward about SkillsJars, a way to manage skill files like dependencies.

James is a wonderful guest, with lots if interesting things to say about programming and AI. I hope you like this episode!

Description

Skills are a great way to bring specific knowledge into your AI, but how do you manage your skill.md files? Wouldn’t it be nice if we could manage them like dependencies, so we could version them, scan for security problems, etcetera. James Ward created SkillsJars to do just that! In this episode he walks us through skills, managing skills as dependencies with SkillsJars, how to consume skills in coding assistant and custom agents, and how to publish skills either through the skillsjars.com website or using Maven / Gradle. Watch this episode to learn how to manage your skills.

Chapters

Links

Other episodes

JNation: Java is hot, people are cool

This year I had the opportunity to speak at JNation for the first time. It was a great conference; great speakers, nice people and a very responsive audience!

Getting there

JNation is held in Coimbra, Portugal. It takes some time to get there, but it is well worth it. The conference arranges for shuttles from Porto and Lisbon to Coimbra; I opted for Porto as it was a shorter flight and drive. At the Porto airport, I ran into Simon Schrottner, who I had met at Devoxx Morocco last year. It turned out we were on the same shuttle bus. We also picked up Martijn Verburg and his cousin Bella from the train station on our way to Coimbra. We had some interesting conversations on the way, which we continued over lunch once we made it to the hotel. While we were there, several other speakers also arrived.

Speaker dinner

The conference organised a speaker dinner the evening before. Andres Almiray, Patrick Baumgartner, Simon and I decided to walk there. This was a bit of an adventure, as the hotel we were staying at was next to a highway which we had to cross…

The speaker dinner is a good opportunity to see the other speakers. Fortunately, my colleague Anton Arhipov was also speaking; it is always nice to see him. And I ran into Sam Aaron, who I hadn’t seen in a while. To top it off, I had the opportunity to hang out with my friend Ewa.

Josh Long told me that he had some feedback on IntelliJ IDEA, and from my side I wanted to show him some new features we had been working on. After we got back from the dinner, we spent some time in the hotel lobby hunched over a laptop.

Conference day

The conference started with some live coded music by Sam Aaron, the creator of Sonic Pi.

The conference was officially opened by Roberto Cortez and team, followed by a keynote by Martijn. After that I had a little time to prepare for my talk, like finding the room where I would be speaking…

Speaking about IntelliJ IDEA

My talk was Be more productive with IntelliJ IDEA, where I live demo features in IntelliJ IDEA. Some features have been there for ages, but I also like to include new features that were added recently, like command completion, and even features that we are still working on for the upcoming release, like logpoints. The room was full, with some people even standing in the back, and the audience was lovely!

You can watch the other talks from JNation 2026 on YouTube.

The hallway track, with extra snacks

After my talk, I had some time to explore the venue some more and talk to people. Some of my friends were staffing a booth with their company, so I went to find them. Also, I spent some time in the speaker room, which was nice and cool. This is a good place to get some work done, or talk to other speakers. Walking around the venue is also a good way to meet people, and get feedback either on our products or my talk, or hear what people are working on.

There were plenty of food and snacks, including some delicious pastéis de nata as well as ice cream, which was very welcome in the hot weather! To get some of the snacks, you needed tokens which you could get by speaking to sponsors at the booths. (Thanks Michał for some extra tokens.)

Star shaped pastéis de nata on a white plate.
Pastéis de nata
Flyers with pictures of ice cream, waffles, brigadeiro and brownie, and the text "JNation teams get tour tokens at the info desk".

Livestream with Josh Long

Josh had invited me to come on his podcast, Coffee + Software. We had a lovely on-air conversation, which was also joined by our friend Daniel Garnier-Moiroux in the chat.

Interview with Andres Almiray

Andres Almiray was at JNation not as a speaker, but as an interviewer. He set up interviews with the speakers in the courtyard of the venue. Among other things, we spoke about some IntelliJ IDEA features, including the upcoming logpoints feature as an entry point to the debugger. Logpoints allow you to add logging to your application running in debug more, without having to change the code and redeploy your application. This will make it easier to start your investigation when debugging issues. It is built on top of the debugger, so you can expand your investigation with additional debugger features as needed.

You can watch the other interviews on the JNation YouTube channel.

After party and another dinner

The conference ended with an after party, with more music by Sam, and drinks with friends in the sun. From the party, we walked to a restaurant for another dinner arranged by the organisers. The food here was great, as was the company. This time I managed to get some pictures with Sam.

Marit van Dijk wearing a black IntelliJ IDEA t-shirt and and Sam Aaron wearing a dark blue JNation t-shirt. Marit is sticking out her tongue and Sam has his thumb up.
Marit van Dijk and Sam Aaron at JNation

Conclusion

Even though it is a little hard to get to, I really enjoyed the conference. The lineup was great, the organisers take good care of the speakers, and I would highly recommend speaking at or attending this conference in the future!

Thanks Roberto Cortez, Bruno Baptista and all of the organisers and volunteers for a great event!

Marit van Dijk wearing a black IntelliJ IDEA t-shirt and sunglasses, standing in front of a huge red JNation banner.
At JNation

GeeCON 2026: Kraków and the Java community

Just over a month ago, I had the pleasure of speaking at GeeCON 2026 in Kraków, Poland. GeeCON is one of my favourite Java conferences, and this year they invited me to join the Program Committee this year along with Marcin Grzejszczak.

Arriving in Kraków

Conferences are a great opportunity to see friends who live abroad. Since Kuba Marchwicki would land in Kraków shortly after me, we agreed to meet up at the airport. He had suggested I should have had a “Welcome to GeeCON” sign ready for him, and fortunately I was able to improvise one on the spot. 

After checking into our respective hotels, we went for lunch at a ramen place which was delicious! Over the meal we had a very interesting conversation about how Kuba manages his “interns”, as he calls his AI agents. It’s interesting to hear how different people are managing their software development process these days.

Conference Day 1

Opening and keynote

The conference was opened by Adam Dudczak, followed by the opening keynote, How To Be a Rockstar Developer by Dylan Beattie, who delivered the entire keynote barefoot. As he described on his blog, a taxi had run over his foot on the way to the venue, and he was not able to put on his boots… Despite the injury, it was an excellent keynote, and he even managed to get the Polish audience to sing along at one point. 

Meeting people

One of the best things about conferences is meeting people. It was nice to finally meet Marcin Grzejszczak in person; I wasn’t sure we had actually met face to face before, despite working together on the programme committee. I also got to meet Tom Akehurst, the creator of WireMock! It was also lovely to see former colleague Ida again, as well as many others… Conversations and connections are what make in person conferences so valuable.

Talks and panels

Generally I prioritize the hallway track over attending talks. One talk I managed to attend was Concurrency Testing on the JVM by Adam Warski. He covered Lincheck and Fray; two tools that instrument bytecode to give you more confidence in your concurrent code. It was really interesting, and I shared with my colleagues who work on Lincheck that he mentioned their tool, which they appreciated!

In the afternoon, I had the honour of moderating the Java panel, where I got to ask Johannes Bechberger, Steve Poole, Piotr Przybył and Gerrit Grunwald what excites them most about Java in 2026. It was a great discussion, and well received.

Unfortunately, the panel was at the same time as Arjen Poutsma‘s talk Teaching an Old Pet Clinic New Tricks: Introducing Agents into Existing Applications. Arjen is a Spring legend (and a fellow Dutchie), so it was wonderful to see him at GeeCON, even if I had to miss his talk. I’ll have to catch up with the recording!

Speaker dinner

In the evening, Piotr and I met up beforehand and walked into town together before joining Kuba for the speaker dinner. We met a bunch of other speakers including Emanuel, one of Marcin’s mentees. It turned out Dylan was not done yet with his back luck; he managed to break some wine glasses at dinner… Other than that it was a wonderful evening with great food, excellent company and interesting conversations. 

Conference Day 2

On day 2 it was time for our talk, Learning modern Java the playful way. This talk is one of my favorites. We usually try to localize it a little for the country where we are presenting. When speaking in Poland, we have a few extra Polish things that Piotr likes to add (see if you can spot them!). Even though I had updated my Polish progress bar, I realised midway during the talk that I had installed it on a different version of IntelliJ IDEA, so it failed to make an appearance this time… 🤦‍♀️

This time, I managed to catch François Martin‘s talk 82 Bugs I Collected in a Year You Won’t Believe Made It to Production, which I liked a lot. I always appreciate good stories about software bugs, and was very amused to hear that François had been collecting them for a while. In fact, I think I might need to do the same…  🤔

When talking to François afterwards, he mentioned he would have loved to join a panel. He suggested that next time we ask speakers before the conference who would be interested to join a panel on a specific topic. Since it turned out that we were short a panelist for the upcoming panel on AI coding, François was able to join that session.

Dinners, discussions and a silly idea

The GeeCON crew take good care of the speakers, so there was another dinner on the second day. This was another chance to hang out with folks, like Adrian, Adam, Łukasz, Rustam, Alex, and others. Based on Dylan’s keynote, Kuba and I had a silly idea; over dinner, several people ended up giving us some excellent input for this topic. (No spoilers yet, as I’m not sure how far we will take this idea…) 

Exploring Kraków

Over the weekend, I had some time to explore in and around the beautiful city of Kraków. 

On Saturday, Spencer Gibb, Tom Akehurst, Jonathan Vila and I booked a guided excursion to the Wieliczka Salt Mine. While waiting for the bus to salt mine at the bus station, we saw a Kevlin Henney on the screen. Which was extra funny considering François’ talk about bugs, so I made sure to send him a picture.

The salt mine was a very impressive place to visit. My favorite were the chandeliers made entirely out of salt crystals. It did involve quite a bit of walking, so we were pretty tired by the end. 

Spencer Gibb, Tom Akehurst, Jonathan Vila, Marit van Dijk and Spencer Gibb at Wieliczka Salt Mine.

For dinner that evening, Spencer and I had pierogi at a restaurant recommended by both a friend of mine and his hotel, which was an excellent tip. 🥟

Pierogi

On Sunday, I visited Wawel Castle and had more pierogi for lunch, before heading home.

Thank you!

Many thanks to Adam Dudczak, Adrian Nowak and the whole team of organisers, volunteers, sponsors, speakers and attendees for putting on another wonderful edition of GeeCON. And a special thank you to Adam and Adrian for having me on the Programme Committee; it was a privilege. It was great to see friends old and new, and I’m already looking forward to the next one!

In the mean time, have a look at the videos and photos from this year.

Nulls are dead – Moritz Halbritter | IntelliJ IDEA Tech Talks

In the first episode of IntelliJ IDEA Tech Talks, I talk to Moritz Halbritter from the Spring team about JSpecify.

We talk about what JSpecify is, and Moritz shows us how to add JSpecify to a codebase. We had a lot of fun recording this episode; I hope you will enjoy the recording!

Description

Null pointer exceptions have been called the billion dollar mistake. They are a common source of bugs and frustration. JSpecify aims to fix that, and with Spring Boot 4 and Spring Framework 7 now fully on board, it’s time to take a closer look. In this episode, Moritz Halbritter from the Spring team walks us through what this means for your Spring projects and how to adopt JSpecify in practice. Using a live demo, we migrate an existing Spring Boot application, tackling problems along the way. See how to use JSpecify for the contract, IntelliJ IDEA for the developer experience, Spring for the framework, and NullAway for the build guarantee. Whether you’re maintaining a large codebase or publishing a library, this episode gives you the tools to start eliminating null pointer exceptions in your applications.

Chapters

  • 00:00:00 – Intro
  • 00:01:09 – What is JSpecify?
  • 00:03:21 – Adding JSpecify to your application
  • 00:08:23 – Add NullAway plugin to check for nullability in the build
  • 00:15:25 – Adding NullMarked to your code
  • 00:18:38 – Fixing false positives
  • 00:33:45 – Using IntelliJ IDEA to find nullability problems
  • 00:38:47 – Using JSpecify with Kotlin
  • 00:45:13 – Adding null checks if you don’t have any
  • 00:51:36 – Summary

Links

Other episodes

Updating a vibe-coded plugin: The Polish progress bar

Polish progress bar

Last year, I vibecoded a plugin as a joke for a talk at Devoxx Poland. We have also used the same progress bar at other conferences in Poland since…

As we were speaking in Poland again at GeeCON, I wanted to reinstall the plugin. 

Unfortunately it turns out that the original project no longer builds. This might be because the version of Gradle it uses is too old (7.x instead of the current v9), because of changes in the IntelliJ platform, or both.

Fortunately, I could ask my colleague Jakub Chrzanowski for help.

Restart from scratch

As it turns out, it was easier to start a project from scratch with the help of a new template.

There are currently 2 ways ways to start a new project:

  • From the Plugin generator website
  • From inside the IDE – This option is available if you have the Plugin Devkit installed in your IDE and will have the same result as creating a project from the website, as they share the same generator.
New project: polishprogressbar

Since I figured it might be easier to start from scratch, I had created a new project using the Plugin generator website. To update the project, we copied the `src` folder from the old project to the new project.

Building and running

The template project comes with several run configurations that you can use to build and verify your project: 

  • Run Plugin will run the plugin, opening a sandbox IDE where you can try your plugin.
  • Run Verifications which will run verifications on the previous, current and upcoming versions of our IDEs (currently: 2025.3, 2026.1 and 2026.2)
  • Run tests will run any tests. (I am ashamed to say this project has none. In my defense, this is a simple plugin and the correct behaviour can be easily verified by running it in the sandbox IDE).   
Run Configurations for plugins

Code cleanup

Jakub also helped me with cleaning up some code. In addition, I did some cleanup myself, partially based on results from the verifications. Restarting the project was a good opportunity to make it a little nicer, and actually care about the code quality a little. 

Installing the plugin

After building the plugin, I installed it on my IDE.

Polish progress bar in action

The plugin is not published to the JetBrains MarketPlace, as I am not sure another progress bar is really needed. You can find the code here.  If you want to build and install it yourself, you can find the instructions in the README.

Thanks to Jakub Chrzanowski for his help with the plugin and this blogpost. ❤️