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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.

read3 min views1 publishedSep 7, 2026
Java Annotated Monthly – September 2026
Image: Blog (auto-discovered)

IntelliJ IDEA #

IntelliJ IDEA – the Leading IDE for Professional Development in Java and Kotlin

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, takes a closer look at upcoming JEPs and shares her key findings on what may be next for Java. Let’s dive in!

September is here, and so is 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). 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), 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 wrote a solid Java 27 breakdown, and if video is more your thing, Catherine Edelveis covers the whole release here.

Still on Java 8 or 11?

Don’t jump, hop. Start now, LTS by LTS, and read my article 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:

- [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/)

That’s it for today! We’re always collecting ideas for the next Java Annotated Monthly – send us your suggestions via email or X by September 20. Remember to check out our archive of past JAM issues for any articles you might have missed!

Subscribe to IntelliJ IDEA Blog updates

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