Java Annotated Monthly – September 2026

JetBrains' September 2026 Java Annotated Monthly highlights the release of JDK 27, which includes nine JEPs, with compact object headers enabled by default (JEP 534) reducing heap usage by 10%–20% and boosting throughput by 5%–10%, and G1 becoming the default garbage collector everywhere (JEP 523). The newsletter also features Kotlin updates, including the Kotlin Benchmark for AI Coding Agents, and articles on AI in software development.

IntelliJ IDEA IntelliJ IDEA – the Leading IDE for Professional Development in Java and Kotlin Java Annotated Monthly – September 2026 This month’s Java Annotated Monthly brings you the latest Java news, a generous dose of AI-focused articles, Kotlin updates, and highlights from a variety of technologies and frameworks, plus plenty more worth adding to your reading list. Our featured writer, Aicha Laafia https://www.linkedin.com/in/aicha-laafia-0266a6126/?locale=fr , takes a closer look at upcoming JEPs and shares her key findings on what may be next for Java. Let’s dive in Featured Content September is here, and so is JDK 27 https://openjdk.org/projects/jdk/27/ . Nine JEPs if you count the previews, and nothing to rewrite unless you are using preview features. Honestly? That’s my favorite kind of release. You upgrade the version, and your app gets faster. The features that change your numbers Compact object headers are on by default JEP 534 https://openjdk.org/jeps/534 . Headers shrink from 96 bits to 64, cutting heap usage by 10% – 20% and pushing throughput up by 5% – 10%. G1 also becomes the default garbage collector everywhere JEP 523 https://openjdk.org/jeps/523 , even on the small machines that used to get Serial GC instead, so check your smallest containers before you upgrade. For the full tour, Sven Woltmann https://www.linkedin.com/in/sven-woltmann wrote a solid Java 27 breakdown https://www.happycoders.eu/java/java-27-features/ , and if video is more your thing, Catherine Edelveis https://www.linkedin.com/in/cat-edelveis/ covers the whole release here https://www.youtube.com/watch?v=VxN-jrjF GA . Still on Java 8 or 11? Don’t jump, hop. Start now, LTS by LTS, and read my article Jurassic JDK: Migrate or Extinct https://foojay.io/today/jurassic-jdk-migrate-or-extinct/ first. I covered everything I wish someone had told me before my first migration. Enjoy this month’s Java Annotated Monthly Java News See what’s new, changing, and coming next in the world of Java: Java Tutorials and Tips Sharpen your Java skills with practical tutorials, clever techniques, and tips worth trying: Kotlin Corner Step into Kotlin Corner for fresh updates: - When Escape Routes Become Toll Roads: Mapping How Developers Move Between Programming Languages https://blog.jetbrains.com/research/2026/08/programming-language-migration/ - KotlinLLM is Going Open Source https://blog.jetbrains.com/research/2026/07/kotlinllm-open-source/ - Introducing the Kotlin Benchmark for AI Coding Agents https://blog.jetbrains.com/kotlin/2026/07/introducing-the-kotlin-benchmark-evaluate-ai-coding-agents-on-real-world-kotlin-tasks/ AI Catch up on the AI ideas, tools, and experiments shaping how developers build software: Languages, Frameworks, Libraries, and Technologies Explore what’s moving and shaking across languages, frameworks, libraries, and the wider tech landscape: - This Week in Spring 1 https://spring.io/blog/2026/08/04/this-week-in-spring-august-4-2026 , 2 https://spring.io/blog/2026/08/11/this-week-in-spring-august-11-2026 , 3 https://spring.io/blog/2026/08/18/this-week-in-spring-august-18-2026 , 4 https://spring.io/blog/2026/08/25/this-week-in-spring-august-25 - Pods as Workers, Not Agents: Rethinking the Deployment Unit for AI Agents on Kubernetes https://www.infoq.com/news/2026/08/pod-deployment-unit-ai-agents/?utm campaign=infoq content&utm source=infoq&utm medium=feed&utm term=global - Gradle Is Going Agentic https://blog.gradle.org/gradle-is-going-agentic - When @Immutable Made All the Difference: A 3.2x Speedup with Hibernate Second-Level Cache https://in.relation.to/2026/08/19/hibernate-immutable-2lc-9x-speedup/ - Vibe Coding, Maven, and the Dependencies You Didn’t Choose https://foojay.io/today/vibe-coding-maven-and-the-dependencies-you-didnt-choose/ Conferences and Events Mark your calendar with the conferences, meetups, and events worth showing up for: - Kansas City Developer Conference https://www.kcdc.info – Kansas City, USA, September 9–12 - JCConfTaiwan https://jcconf.tw/2026/ – Taipei, Taiwan, September 11 - Java Forum Nord https://javaforumnord.de/2026/ – Hannover, Germany, September 22 - JUG Saxony Day https://jugsaxony.org/day/ – Radebeul, Germany, September 25 - Confitura https://2026.confitura.pl – Warsaw, Poland, September 25–26 - GOTO Copenhagen https://gotocph.com/2026 – Copenhagen, Denmark, September 28 – October 2 Culture and Community Check out these stories about what makes the developer community tick. And Finally… Check out the latest articles by the IntelliJ IDEA team: - The Grails Plugin Has a New Home: Apache Grails https://blog.jetbrains.com/idea/2026/09/the-grails-plugin-has-a-new-home-apache-grails/ - Println Debugging Done Right https://blog.jetbrains.com/idea/2026/08/println-debugging-done-right/ - Spring Boot Configuration Management Best Practices https://blog.jetbrains.com/idea/2026/08/spring-boot-configuration-management-best-practices/ - Project Loom in IntelliJ IDEA: Virtual Threads, Scoped Values, and Structured Concurrency https://blog.jetbrains.com/idea/2026/08/project-loom-in-intellij-idea-virtual-threads-scoped-values-and-structured-concurrency/ That’s it for today We’re always collecting ideas for the next Java Annotated Monthly – send us your suggestions via email https://mail.google.com/mail/u/0/?fs=1&tf=cm&source=mailto&to=JAM@jetbrains.com or X https://x.com/intellijidea?ref src=twsrc%5Egoogle%7Ctwcamp%5Eserp%7Ctwgr%5Eauthor by September 20. Remember to check out our archive of past JAM issues https://www.jetbrains.com/lp/jam/ for any articles you might have missed Subscribe to IntelliJ IDEA Blog updates