Kotlin Language JVM and Android Goes GA

• By John K. Waters
• February 16, 2016

Software development toolmaker JetBrains has announced the general availability of Kotlin 1.0, its open source programming language for both JVM and Android. The language has been in development for more than five years and used in production for the last two years. The company published the 1.0 beta release candidate in November of last year.

Kotlin is a statically typed language similar to Scala, Gosu, Ceylo and Fantom. It compiles to both JVM byte code and JavaScript. JetBrains, maker of the code-centric Java IDE, IntelliJ IDEA, began developing the language in 2010, and the company uses Kotlin in production of that IDE and other products. JetBrains has claimed that the language is more stable at runtime than Java, because it can statically check weak points and supports things like variable type interface, closures, extension functions, and mix-ins.

"If I were to choose one word to describe Kotlin's design, it would be pragmatism," said project lead Andrey Breslav in a company blog post. "This is why, early on, we said that Kotlin is not so much about invention or research. We ended up inventing quite a few things, but this was never the point of the project. Of course we were building a type system that prevents bugs, and abstraction mechanisms that facilitate code reuse, as anybody in our position would. But our (pragmatic) way of doing it was through focusing on use cases to make the language a good tool."

Prague-based JetBrains released Kotlin in July 2011 for distribution under the Apache 2 Open Source License. "We know that Java is going to stand long, but we believe that the community can benefit from a new statically typed JVM-targeted language free of the legacy trouble and having the features so desperately wanted by the developers," Breslav told ADTmag at the time.

JetBrains is the primary backer of Kotlin. The company has committed 20 JetBrains employees to the project, it said, and nearly 100 collaborators are working on the language. "[W]e have invested a lot of effort into developing it and we are committed to the project for the long run," Breslav said. "We wrote it out of our own need to use in our own products." The language is used in production at JetBrains and by other organizations and individual developers "from web-service back-ends to Android apps," Breslav has said. Several JetBrains products are using Kotlin today, including IntelliJ IDEA, JetBrains Rider, JetBrains Account & E-Shop, and YouTrack, as well as some internal project, Breslav said.

Kotlin saw strong adoption before the GA release. The company claims more than 11,000 users in January. Two books have been written about the language: Kotlin in Action and Kotlin for Android Developers.

A list of some Kotlin users, including a short note explaining how they're using it, is available on GitHub.