Version 1.2 of the statically typed Kotlin language, a version of Java endorsed by Google for Android app development, offers an experimental feature enabling reuse of code across platforms, as well as compatibility with the Java 9 module system.
With the 1.2.20 update released January 17, Kotlin adds a number of capabilities in areas ranging from use of the Gradle build system to building Android mobile applications. Described as a bug fix and tool update, version 1.2.20 includes:
- Gradle build cache support.
- Performance improvements as well as new inspections and bug fixes in the IntelliJ IDEA plugin for Kotlin.
- Improvements to incremental compilation for Android and mixed Java/Kotlin projects.
- IDE backing for the new Kotlin style guide, which covers formatting of code and idiomatic use of language and library capabilities.
This update is compatible with IntelliJ IDEA IDE from 2017.1 to 2017.3. It also works with the Android Studio IDE versions 3.0 and 3.1.
Where to get Kotlin 1.2
Kotlin 1.2 is bundled with JetBrains’ IntelliJ Idea 2017.3 IDE, which will be released by December 1. Users of the Android Studio IDE or an older version of IntelliJ can update to the new version via Tools > Kotlin > Configure Kotlin Plugin Updates.
The new features in Kotlin 1.2
Developers can express dependencies of common code on platform-specific parts via expected and actual declarations. This declaration specifies an API, while an actual declaration is either platform-specific to the API or a type alias that refers to an existing implementation of the API in an external library. The standard library, meanwhile, features the kotlin.math package for performing mathematical operations in cross-platform code.
Kotlin 1.2’s standard library is compatible with newly introduced Java 9 module system, which forbids split packages (multiple .jar files declaring classes in the same package). In Kotlin 1.2, the
kotlin-stdlib-jdk8 artifacts replace the old
Also to support Java 9, Kotlin 1.2 also removes the deprecated declarations in the
kotlin.reflect package from the
kotlin-reflect library. Developers need to switch to using the declarations in the
kotlin.reflect.full package, which debuted in Kotlin 1.1.
Type inference improvements in Kotlin 1.2 include enabling the compiler to use information from type casts in type inference. If a developer calls a generic method that returns a type parameter, such as
T, and casts the return value to a specific type, such as
Foo, the compiler now understands that
T for this call needs to be bound to the type
Foo. This is especially important for Android developers, for the Kotlin compiler to correctly analyze
findViewById calls in Android API Level 26. Also, the compiler now has an option to treat all warnings as errors.
Kotlin 1.2 also has these enhancements:
- It now supports array literals in annotations, simplifying coding.
- It uses a more consistent syntax.
- The new reflection API lets developers check whether a
lateinitvariable has been initialized.
lateinitmodifier now can be used on top-level properties and local variables.