Kotlin M3 brings important additions to fledgling JVM language

It’s been a quiet few months for the upcoming JVM language set to be launched by JetBrains, the creators behind the wildly successful Java IDE, IntelliJ IDEA. But for good reason – they’ve been working hard towards the third milestone of statically-typed Kotlin.

The JVM bytecode and JavaScript compiling effort has been in the works since July 2011 and appears to be nearing its curtain call with the latest update. Aside from a fresh lick of paint to Kotlin’s website and over 400 issues closed, important additions have been made to the language itself.

Andrev Breslav, the lead for Kotlin, last week gave a sneak preview into Kotlin’s new exciting feature of multi-declarations, ideal for writing extension functions. Breslav also informs that, despite not being complete, there’s been huge strides made in the type argument interface algorithm.

He adds (emphasis Breslav’s):

In M3 we started to profile things and tune performance of the IDE as well as the compiler. It will be a lot of work, but eventually everything will be fast and consume little memory. This time most improvements are related to code completion.

Kotlin is rightly trying to stand apart from other JVM languages, and the work done toward collections looks promising, as the java.util diagram below shows. Essentially, there are interfaces that can distinguish between mutable and read-only collections.

Tuples are out, external annotations are in and as of M3, Kotlin supports local classes and object declarations. The team are once again encouraging feedback on their JVM alternative. If you’re new to what Kotlin can do, the Getting Started guide should get you up to speed.

The team will be showcasing what Kotlin can do at the upcoming JavaOne conference, so we should get to see more of what the JVM language can do against its competitors.