Utrecht JUG Meetup – September 16th: From Stream Gatherers to Constraint AI

We’re excited to welcome you back to Utrecht JUG on September 16th, for our first meetup after the summer break, hosted by YOINK. Join us for an evening full of Java, practical insights, great conversations, food, drinks, and plenty of opportunities to reconnect with fellow developers.

We’ll start the evening with food and drinks before diving into our first session, where Hinse ter Schuur presents Level Up Your Java Streams with Gatherers. Since Java 8, the Stream API has become an essential tool for Java developers. Now, Java 24 introduces Stream Gatherers, opening the door to custom intermediate operations. Hinse will explore what Gatherers are, where they shine, and how you can implement your own, giving you practical knowledge to take back to your everyday Java code.

After the break, Tom Cools takes us into the world of constraint optimization with “You May Now Optimize the Wedding”: Optimizing the Seating, Bachelor Party, and Honeymoon with Constraint AI. Using wedding seating, pub crawls, and honeymoon itineraries as examples, Tom demonstrates how Timefold can tackle complex planning problems with real code and constraints.

Please join us and RSVP!

Because of the limited number of seats, please keep your RSVP up-to-date, so we can welcome someone else if you can't make it.

Timeschedule
17:30 Doors open
18:00 Food & Drinks
18:45 Level UP Your Java Streams with Gatherers, by Hinse ter Schuur
19:45 Break
20:00 You May Now Optimize The Wedding by Tom Cools
21:00 Drinks

Giveaway
1 JetBrains licence

Talk

Level Up Your Java Streams with Gatherers

Since Java 8, the Stream API has been a valuable tool for Java developers. However, our hunt for better solutions has often left us wanting more. Until now, we could only use the standard provided intermediate operations on streams, like map, filter, and flatMap. Enter Java 24's new Stream Gatherers, which allow for adding custom intermediate operations to our streams.

In this session you'll learn what Gatherers are, where they shine, and how you can implement your own. By the end of the session, you'll be fully equipped to use this powerful new feature in your day-to-day work.

"You May Now Optimize the Wedding": Optimizing the Seating, Bachelor Party, and Honeymoon with Constraint AI

This talk shows how to automate complex planning problems using constraint optimization. Using wedding scenarios like seating charts, pub crawls, and honeymoon itineraries, it demonstrates how Timefold solves scheduling, routing, and planning challenges with real code and constraints, turning “could I automate this?” into working optimization solutions..

Speakers

Hinse ter Schuur

Hinse is a software developer at SDB Java with over twenty years of experience in Java and several years working with Scala. He enjoys working on code that is meant to be read, understood, and changed, preferably without surprises. His interests lie in language features, APIs, and the design decisions that quietly shape codebases over time. Hinse shares his experience through pair programming, code reviews, writing, and conference talks, with a strong focus on software craftsmanship and pragmatic engineering.

Tom Cools

Developer Relations Engineer for Timefold, Java Champion and co-organizer of the Belgian Java User Group. Tom has a decade worth of experience delivering systems and loves to share not only knowledge but also passion for our craft. You can read more at his blog (http://www.tomcools.be) or follow him on Bluesky (@tomcools.be).