The currently released version is 1.1.4, published on August 15, 2017.
Yes. Kotlin is free, has been free and will remain free. It is developed under the Apache 2.0 license and the source code is available on GitHub.
Kotlin has both object-oriented and functional constructs. You can use it in both OO and FP styles, or mix elements of the two. With first-class support for features such as higher-order functions, function types and lambdas, Kotlin is a great choice if you’re doing or exploring functional programming.
Kotlin is more concise. Rough estimates indicate approximately a 40% cut in the number of lines of code. It’s also more type-safe, e.g. support for non-nullable types makes applications less prone to NPE’s. Other features including smart casting, higher-order functions, extension functions and lambdas with receivers provide the ability to write expressive code as well as facilitating creation of DSL.
Yes. Kotlin is 100% interoperable with the Java programming language and major emphasis has been placed on making sure that your existing codebase can interact properly with Kotlin. You can easily call Kotlin code from Java and Java code from Kotlin. This makes adoption much easier and lower-risk. There’s also an automated Java-to-Kotlin converter built into the IDE that simplifies migration of existing code.
Yes. Kotlin is supported as a first-class language on Android. There are hundreds of applications already using Kotlin for Android, such as Basecamp, Pinterest and more. For more information check out the resource on Android development.
Yes. Kotlin is 100% compatible with the JVM and as such you can use any existing frameworks such as Spring Boot, vert.x or JSF. In addition there are specific frameworks written in Kotlin such as Ktor. For more information check out the resource on server-side development.
Yes. You can use any Java UI framework such as JavaFx, Swing or other. In addition there are Kotlin specific frameworks such as TornadoFX.
Kotlin/Native is currently in the works. It compiles Kotlin to native code that can run without a VM. There is a Technology Preview released but it is not production-ready yet, and doesn’t yet target all the platforms that we plan to support for 1.0. For more information check out the blog post announcing Kotlin/Native.
Kotlin is supported by all major Java IDEs including IntelliJ IDEA, Android Studio, Eclipse and NetBeans. In addition, a command line compiler is available and provides straightforward support for compiling and running applications.
No. Kotlin lets you choose between generating Java 6 and Java 8 compatible bytecode. More optimal byte code may be generated for higher versions of the platform.
There are too many companies using Kotlin to list, but some more visible companies that have publicly declared usage of Kotlin, be this via blog posts, GitHub repositories or talks include Square, Pinterest or Basecamp.
Kotlin is primarily developed by a team of engineers at JetBrains (current team size is 40+). The lead language designer is Andrey Breslav. In addition to the core team, there are also over 100 external contributors on GitHub.
There are already a number of books available for Kotlin, including Kotlin in Action which is by Kotlin team members Dmitry Jemerov and Svetlana Isakova, Kotlin for Android Developers targeted at Android developers.
There are also many recordings of Kotlin talks available on YouTube and Vimeo.
Yes. There are many User Groups and Meetups now focused exclusively around Kotlin. You can find a list on the web site. In addition there are community organised Kotlin Nights events around the world.
Yes. The first official KotlinConf, taking place in San Francisco 2-3 November 2017. Kotlin is also being covered in different conferences worldwide. You can find a list of upcoming talks on the web site.
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