VoxxedDays 2026

So, I went to VoxxedDays on April 1st and 2nd.¹

Some of it was very interesting, and I've retained some notes and links written below.

Spec-driven development²

It seems to be a way to specify the wanted behaviour of your software in such a way that AI can successfully create your software based on your spec. Not entirely convinced of this.

Lion³

Lion is a set of highly performant, accessible and flexible Web Components.

PicNic⁴

PicNic is a online greengrocer/supermarket which is running a Blog on the challenges on scaling up. Quite interesting.

Some interesting things for example are providing fresh products (bread for instance) within a certain timeframe.

Programming Rules your IDE can tell you about.

https://github.com/jborgers/PMD-jPinpoint-rules

Compressed OOPs in the JVM

https://www.baeldung.com/jvm-compressed-oops

A good explanation of generics

https://bramjanssens.nl/generics/

Reduce Object Header Size and Save Memory in Java 25

https://www.baeldung.com/java-object-header-reduced-size-save-memory

References

[1] VoxxedDays Amsterdam

https://amsterdam.voxxeddays.com/

[2] What Is Spec-Driven Development? A Complete Guide

https://www.augmentcode.com/guides/what-is-spec-driven-development

[3] Github - Ing/Lion

https://github.com/ing-bank/lion

[4] PicNic - Blog

https://blog.picnic.nl/

Kotlin: lots of functions

I like Kotlin (sometimes) as it has a large and rich number of convenient functions to use.

In Java, we tend to reach for our Guava¹ or Apache Commons Lang² to get the same functionality.

But it does tend to make it a bit hard to decide which to use, especially as I (as most people I hope) do not know the entire dictionary of available functions in Kotlin.

Luckily there's of course colleagues who can help, and my IDE also does a pretty good task of suggesting better ways.

Case in point:

val items : List<Items> = getItems()
val coupon: Coupon? = items.map { it.coupon }.filter { it != null }.firstOrNull()

I do know the code above can be made simpler.

val items : List<Items> = getItems()
val coupon: Coupon? = items.mapNotNull { it.coupon }.firstOrNull()

There, the mapNotNull() is a very convenient function that I use all the time.

But this time my IDE complained again and told me to use .firstNotNullOfOrNull

val items : List<Items> = getItems()
val coupon: Coupon? = items.firstNotNullOfOrNull { it.coupon }

It's fine by me, to use this, but I didn't know this function exists.

Also, the name seems a bit long and it took a minute to understand the meaning.

References

[1] GitHub - Google Guava

https://github.com/google/guava

[2] Maven Repository - Apache Commons Lang (3)

https://mvnrepository.com/artifact/org.apache.commons/commons-lang3