[augustl]

Kotlin is a much better Java so that's what we use :)

I have a friend who maintains a gazillion JVM based apps for the Norwegian tax authorities and he's a Kotlin skeptic. He's pretty tired of maintaining and porting various small apps and microservices from arcane old and discarded Scala web frameworks etc. Given how locked-in Kotlin is to a single company, I kind of get his skepticism.

[gorset]

I think the «best practices» found in Java enterprise has meant that a lot of people think all Java has to look like that.

High performance Java is awesome and can be competitive with C++ and Rust for non trivial systems, thanks to much better development cycle, debugging and high quality libraries.

Most the benefits is the JVM, so Kotlin has those too, but I don’t feel Kotlin is enough of an improvement to warrant the downsides (at least for me). But both Kotlin, Scala and Clojure are great for the Java ecosystem.

[jillesvangurp]

Java is controlled by Oracle. It's not that different from Kotlin in that respect. Go is controlled by Google. Swift is controlled by Apple. Typescript, C#, F#, VB, etc. are Microsoft controlled things. It's not like the grass is that much greener next door. I don't think these things are show stoppers. A lot of this stuff is open source after all.

Jetbrains considered using Scala before they created Kotlin. I think they were right. With Kotlin they went for a bit more conservative approach. Mainly undoing things that aren't so great in Java language and unlikely to change for language compatibility reasons, and avoiding some of the pitfalls with Scala. I think Scala saw a bit of wild growth of features and frameworks that Kotlin largely avoided. For better or worse, there has been a bit of a Scala diaspora with people flocking to things like Rust, Elixir, and indeed some to Kotlin.

Weather people like it or not, Kotlin plays very nice with existing Java code bases. By design. It was designed as a drop in replacement. It's why it caught on with Android developers before it even was released. It's a bit different from Scala in that respect, which while it worked alright with Java code bases really nudged you away from that to the point where you'd be swapping out your build tools, frameworks, etc.

At this point Kotlin is arguably a better language to use with any of the popular Java frameworks. I'm not really aware of any exceptions to this. Spring is a good example (arguably the most popular server framework for Java and the JVM). IMHO you are missing out if you are not using that with Kotlin. The Spring people certainly seem to agree. They've invested lots of time and effort to make Kotlin a first class citizen in the ecosystem. Documentation is dual Kotlin/Java, the framework ships with lots of extension functions for Kotlin and Kotlin specific features, and expanded Kotlin support is one of the headline features for the upcoming major version. And it's not like the previous version was particularly lacking on that front. They've been supporting the Kotlin ecosystem for many years now.

[vbezhenar]

I've used Kotlin quite a bit as a Java replacement in the past. However its roadmap was weird for me. I wanted Kotlin to be a thin layer upon Java, however Jetbrains ported it to JavaScript, to native. It felt like lack of focus. Another issue with Kotlin was, that its development did not 100% align with Java. Kotlin co-routines were invented, but Java went into green threads direction instead, so this feature feels like unnecessary complication of already complicated language.

Nowadays I prefer Java. It's not ideal, but it aligns 100% with JVM. Kotlin was good in Java 7 times, when Java development felt frozen.

[elric]

> Java is controlled by Oracle.

That's factually incorrect. Oracle owns the trademarks, but the language proper is governed by the community, most development is done in the open as part of OpenJDK, which is the reference implementation.

[p2detar]

After several years of using Kotlin, I've learned that while it's easy and often a pleasure to write, it can be a nightmare to read and I spend far more time reading code than writing it. I like the language and still use it, but for our flagship product I decided to stick with Java, and I'm glad I did now that it has accelerated the rollout of new language features.

edit: grammar

[peterashford]

I've coded in both. I prefer Java but Kotlin is pretty cool also. And Clojure.