JIjillesvangurp·Feb 6, 2020
Everything Java does (including considering recent updates), Kotlin does better. So no. I made the switch to Kotlin two years ago and I'm not looking back. It doesn't matter what frameworks you use, Kotlin is a drop in replacement for Java. Though obviously, if you are doing greenfield use something that makes the most of the language.
There's this misconception that Kotlin is an Android only thing or a JVM only thing. The reality in both Android and server side frameworks is that the big frameworks are all moving towards being Kotlin friendly/ready. Additionally, Kotlin is rapidly moving towards being a proper full stack language with a native compiler (currently in beta), a javascript transpiler, and lots of other tooling maturing. People are already doing cross IOS/Android libraries in Kotlin.
A big advantage of Kotlin over e.g. Scala
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and other JVM languages that are not Java is that it is designed from the ground up make the transition as seamless as possible. Scala is so far removed from Java that it's generally a completely separate ecosystem with its own libraries, tools, frameworks, idioms, etc. Yes you can use Java stuff but it's generally frowned upon by Scala people.
This is not the case with Kotlin at all. The Android ecosystem started transitioning to Kotlin long before Google recommended that and before Kotlin 1.0 because the pain of having to deal with Java 6/7 just made that development so much better. A few years ago they started endorsing and recommending it and at this point they are clearly deprecating a lot of stuff that they did for Java that can be done better with Kotlin e.g. embracing co-routines over rxjava, adding extension functions and kotlin dsls and designing new features that really only make sense if you use Kotlin. On Android, if you are doing Java, you are working on a legacy code base.
On the server side the same is happening with e.g, Spring, which is basically the dominant server side framework for the JVM. I used Kotlin with Spring Boot 1.x/Spring 4.x, and it was a nice upgrade despite the lack of Kotlin support for it.
With Spring 5 and Spring Boot 2.x they started adding a lot of Kotlin extension functions, co-routine support (which generally makes using their reactive stuff less painful), and there's an experimental project for Kotlin DSL (https://github.com/spring-projects-experimental/spring-fu) to replace the mess of annotations that is currently needed and which reduces the need for reflection, proxies, and other tricks that currently make using Spring with Graal vm hard. Basically, what that means is that if you use Spring in a new project and you are not using Kotlin, you are probably making a mistake because you are missing out on a lot of good stuff. They'll likely not deprecate Java entirely for a long time just because there are a lot of very conservative projects in e.g. banks using Java but if you read between the lines they are basically saying Kotlin is it going forward.
IMHO, the Java language is definitely improving but just not at a pace where it actually keeps up and a lot of the stuff they add is a big compromise compared to what you get in Kotlin. and of course Kotlin is improving as well and a lot of the Java changes (and related JVM changes) also benefit Kotlin.