JVM Language Kotlin M13 Released

Software development toolmaker JetBrains has announced a new milestone release of Kotlin, its open source, JVM-targeted programming language. Milestone Release 13 (M13) comes with a new compiler daemon; new lateinit property to support dependency injection and other frameworks; new .class file layout for top-level functions and properties; sealed classes for expressing closed hierarchies; and better type safety for Java interop, among others.

Kotlin is a statically typed language similar to Scala, Gosu, Ceylon and Fantom. It compiles to both JVM byte code and JavaScript. JetBrains, maker of the code-centric Java IDE, IntelliJ IDEA, has claimed that the language is more stable at run time than Java, because it can statically check weak points and supports things like variable type interface, closures, extension functions and mix-ins.

The Kotlin team is working toward the 1.0 release of the language and will continue to focus on JVM support, said Andrey Breslav, the lead language designer working on Kotlin at JetBrains, in a blog post. "The JavaScript back-end will be included," he wrote, "but it will be considered an experimental feature. Because of that, there are few changes affecting JavaScript in this release. We plan to resume work on JS after the 1.0 release is out."

JetBrains began developing Kotlin in 2010 and released it 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," project lead Andrey Breslav said at the time. The company released the first Kotlin milestone (M1) in April 2012 with a plugin for the JetBrains IntelliJ IDEA dev tool suite.

Breslav noted that the Kotlin libraries are also being actively developed, and the M13 release brings with it a fully functional reflection library, which means "we can now introspect classes, their members, parameters etc.," he said. The standard library gets several improvements, including + and for sets and other collections, and improved delegates for properties.

More details are available on the company blog page, and the language docs page.

About the Author

John has been covering the high-tech beat from Silicon Valley and the San Francisco Bay Area for nearly two decades. He serves as Editor-at-Large for Application Development Trends ( and contributes regularly to Redmond Magazine, The Technology Horizons in Education Journal, and Campus Technology. He is the author of more than a dozen books, including The Everything Guide to Social Media; The Everything Computer Book; Blobitecture: Waveform Architecture and Digital Design; John Chambers and the Cisco Way; and Diablo: The Official Strategy Guide.



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