https://javapro-en.svenruppert.com/tags/interop/Recent content in Interop on JAVAPRO InternationalHugoen-USThu, 07 May 2026 07:00:01 +0000https://javapro-en.svenruppert.com/kotlin-kontra-java-part-3-language-for-interop/Thu, 07 May 2026 07:00:01 +0000https://javapro-en.svenruppert.com/kotlin-kontra-java-part-3-language-for-interop/<p>When you start a new project on the JVM, should you pick Java or Kotlin? Why not both?</p> <p>You can use any Java library you want in Kotlin, you can even co-write your software in both languages (e.g. one team I work with writes their JUnit tests in Kotlin, their main code in Java) and migrate to Kotlin or back to Java over time. <a href="https://kotlinlang.org/docs/java-interop.html">Kotlin is designed with Java interoperability in mind</a>, because JetBrains wanted to migrate their IDEs (IntelliJ IDEA, WebStorm, etc.) incrementally to the language. But how does that work? What does Kotlin do, so that interop to this degree becomes possible?</p>