What we're about

The primary focus of The Belgium Java User Group (founded in 1997 by Stephan Janssen) is to inform our members about the Java ecosystem.
We regularly organise free sessions for Java and JVM interested developers, devops and teamleads to socialize, learn and inspire.

Interested to contribute and participate in our vibrant and independent Java community here in Belgium? Reach out to the team! We are always looking for new speakers and Meetup Hosts.

Upcoming events (1)

What the CRaC - Superfast JVM startup

Sweet Mustard

Greetings everyone!

For our next event, we are heading to West Flanders! We welcome you to Kortrijk at SweetMustard (check them out at: sweetmustard.be).

We also want to try out something new. Do you want to speak about anything Java and/or developer related? We reserve the first hour for a few short talks! Please, send us your proposal via this GitHub issue. Be warned! If you don't do it, the organizers will talk too long about BeJUG, Foojay.io, #JavaOnRaspberryPi, etc. ;-)

In the next hour, we welcome Gerrit Grunwald "on the stage"! Are you sick of trying to improve JVM startup times when running your app in microservice environments? Are you wondering what enabled AWS to build Lambda SnapStart? Attend this session and see how you can start up your JVM-based application in milliseconds without using native images but only pure JVM combined with CRaC.

Today's topic

In a world where microservices are more and more a standard architecture for Java-based applications running in the cloud, the JVM warmup time can become a limitation. Especially when you look at spinning up new instances of an app as a response to changes in load, the warmup time can be a problem. Native images are one solution to solve these problems because their statically, ahead-of-time compiled code simply doesn’t have to warm up and so has a short startup time. But even with the shorter startup time and the smaller footprint, it doesn’t come without a drawback. The overall performance might be slower because of the missing JIT optimizations at runtime. There is a new OpenJDK project called CRaC (Coordinated Restore at Checkpoint), which aims to address the JVM warmup problem with a different approach. The idea is to take a snapshot of the running JVM, store it in files and restore the JVM at a later point in time (or even on another machine).

This session will give you a short overview of the CRaC project and shows some results from a proof of concept implementation.

About our speaker

Gerrit Grunwald is a software engineer that loves coding for around 40 years already. He is a true believer in open source and has participated in popular projects like JFXtras.org and his own projects (TilesFX, Medusa, Enzo, SteelSeries Swing, SteelSeries Canvas, JDKMon).

Gerrit blogs regularly at harmonic-code.org, he is an active member of the Java community, where he founded and leads the Java User Group Münster (Germany), he is a JavaOne rockstar and a Java Champion. He is a speaker at conferences and user groups internationally and writes for several magazines.


  • 18:00: Doors + food
  • 19:00: Short sessions
    - You have a topic? Let us know!
    - BeJUG updates and info
    - Do you know foojay.io, the website for Friends Of OpenJDK?
    - Having fun with Java, JBang and Pi4J on the Raspberry Pi
  • 20:00: What the CRaC - Superfast JVM startup

Additional note: This meetup includes food. We, therefore, ask you to please keep your RSVP status up to date, so we do not waste any of our food.

Past events (12)

Quarkus 101: Intro To Java Development With Quarkus

Ordina Belgium

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