Kotlin Programming Language
Some handy links:
- Kotlin Site
- Getting Started Guide
- Try Kotlin
- Kotlin Standard Library
- Issue Tracker
- Kotlin YouTube Channel
- Kotlin Blog
- Subscribe to Kotlin YouTube channel
- Follow Kotlin on Twitter
- Public Slack channel
- TeamCity CI build
Kotlin Multiplatform capabilities
Support for multiplatform programming is one of Kotlin’s key benefits. It reduces time spent writing and maintaining the same code for different platforms while retaining the flexibility and benefits of native programming.
- Kotlin Multiplatform Mobile for sharing code between Android and iOS
- Getting Started with Kotlin Multiplatform Mobile Guide
- Kotlin Multiplatform Benefits
- Share code on all platforms
- Share code on similar platforms
Build environment requirements
Unfortunately AdoptOpenJdk project does not provide required JDK 1.6 and 1.7 images, so you could either download them manually and provide path to installation via
JDK_1_7 environment variables or use following SDK managers:
Alternatively, it is still possible to only provide required JDKs via environment variables (see gradle.properties for supported variable names). To ensure Gradle uses only JDKs from environmental variables - disable Gradle toolchain auto-detection by passing
-Porg.gradle.java.installations.auto-detect=false option (or put it into
For local development, if you're not working on the standard library, it's OK to avoid installing JDK 1.6 and JDK 1.7. Add
kotlin.build.isObsoleteJdkOverrideEnabled=true to the
local.properties file, so build will only use JDK 1.8+. Note, that in this case, build will have Gradle remote build cache misses for some tasks.
Note: The JDK 6 for MacOS is not available on Oracle's site. You can install it by
$ brew tap homebrew/cask-versions
$ brew install --cask java6
On Windows you might need to add long paths setting to the repo:
git config core.longpaths true
The project is built with Gradle. Run Gradle to build the project and to run the tests using the following command on Unix/macOS:
or the following command on Windows:
On the first project configuration gradle will download and setup the dependencies on
intellij-coreis a part of command line compiler and contains only necessary APIs.
idea-fullis a full blown IntelliJ IDEA Community Edition to be used in the plugin module.
These dependencies are quite large, so depending on the quality of your internet connection you might face timeouts getting them. In this case, you can increase timeout by specifying the following command line parameters on the first run:
./gradlew -Dhttp.socketTimeout=60000 -Dhttp.connectionTimeout=60000
Important gradle tasks
clean- clean build results
dist- assembles the compiler distribution into
install- build and install all public artifacts into local maven repository
coreLibsTest- build and run stdlib, reflect and kotlin-test tests
gradlePluginTest- build and run gradle plugin tests
compilerTest- build and run all compiler tests
To reproduce TeamCity build use
-Pteamcity=true flag. Local builds don't run proguard and have jar compression disabled by default.
OPTIONAL: Some artifacts, mainly Maven plugin ones, are built separately with Maven. Refer to libraries/ReadMe.md for details.
To build Kotlin/Native, see kotlin-native/README.md.
It is recommended to use the latest released version of Intellij IDEA (Community or Ultimate Edition). You can download IntelliJ IDEA here.
After cloning the project, import the project in IntelliJ by choosing the project directory in the Open project dialog.
For handy work with compiler tests it's recommended to use Kotlin Compiler Test Helper
We have a dependencies verification feature enabled in the repository for all Gradle builds. Gradle will check hashes (md5 and sha256) of used dependencies and will fail builds with
Dependency verification failed errors when local artifacts are absent or have different hashes listed in the verification-metadata.xml file.
It's expected that
verification-metadata.xml should only be updated with the commits that modify the build. There are some tips how to perform such updates:
verification-metadata.xmlto avoid stockpiling of old unused dependencies. You may use the following command:
sed -i '' -e '/<components>/,/<\/components>/d' gradle/verification-metadata.xml
#Linux & Git for Windows
sed -i -e '/<components>/,/<\/components>/d' gradle/verification-metadata.xml
- Re-generate dependencies with Gradle's
--write-verification-metadatacommand (verify update relates to your changes)
./gradlew -i --write-verification-metadata sha256,md5 -Pkotlin.native.enabled=true resolveDependencies
resolveDependencies task resolves dependencies for all platforms including dependencies downloaded by plugins
- If you’re adding a dependency with OS mentioning in an artifact name (
windows), remember to add them to
implicitDependenciesconfiguration or update
resolveDependenciestask if needed.
resolveDependenciesshould resolve all dependencies including dependencies for different platforms.
Using -dev and -SNAPSHOT versions
-SNAPSHOT versions frequently.
-dev versions you can use the list of available versions and include this maven repository:
-SNAPSHOT versions that are updated daily, you can use the list of available versions and include this maven repository:
Kotlin is distributed under the terms of the Apache License (Version 2.0). See license folder for details.
Please be sure to review Kotlin's contributing guidelines to learn how to help the project.