inline to switch back to the classic concatenation via StringBuilder.append().

indy to perform invokedynamic concatenation on strings with StringConcatFactory.makeConcat().

indy-with-constants to perform invokedynamic concatenation on strings with StringConcatFactory.makeConcatWithConstants() (this is planned to be default for JVM 9+ targets in 1.5).

To enable invokedynamic string concatenation, add the -Xstring-concat compiler option with one of the following values:

String templates, except for those with a single non-constant argument (see KT-42457).

us in the operator ( a + b), explicit ( a.plus(b)), and reference ( (a::plus)(b)) forms.We have started to implement this mechanism in Kotlin for better performance, and it can now compile string concatenations into dynamic invocations on JVM 9+ targets.Ĭurrently, this feature is experimental and covers the following cases: This works faster and consumes less memory than the previous implementation, and it leaves space for future optimizations without requiring bytecode changes. Since Java 9, the string concatenation on the JVM has been done via the dynamic method invocation (the invokedynamic instruction in the bytecode).

On the JVM, we’ve added the new JVM 15 target and mostly focused on improving existing functionality and performance, as well as fixing bugs.

Now let’s dive into the details! Kotlin/JVM The complete list of changes is available in the change log.Īs always, we’d like to thank our external contributors who helped us with this release. You can also find a brief overview of the release on the What’s new in Kotlin 1.4.20 page in Kotlin docs. Read on to learn more about the features of Kotlin 1.4.20. So if you encountered problems with any of those features, now’s a good time to give them another try. We are also shipping numerous fixes and improvements for existing features, including those added in 1.4.0.

Extensions for JDK Path: Path('dir') / 'file.txt'.Improved performance and exception handling for KMM projects.Support for new JVM features, like string concatenation via invokedynamic.Give them a try and share your feedback on Slack (get an invite here) or YouTrack. Being open to community feedback is one of the Kotlin team’s basic principles, and we need your thoughts about the prototypes of the new features. Kotlin 1.4.20 is here with new experimental features for you to try.

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