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The interesting thing - from a performance point of view - of the 2025 Feature Face-off is that the performance features totally dominated. Half the entries were performance related features which already shows you how important performance is, and the winner in each of the four categories was one of the performance related features. Not just the winner, but where there was more than one performance feature in the category, the runner up was also a performance feature. It's clear that if you want to win a feature face-off, being a performance feature gives you a huge advantage.

In both the "Language" and "Tooling" sections, the winner is the sole performance related feature in each category: Records (performance related because of their immutability), and JDK Mission Control.
In "Libraries" half the entries are performance features, including both the winner and runner up: Structured Concurrency and Sequenced Collections.
In "Runtime" six of the eight entries are performance features, so it's unsurprising that the winner (Virtual Threads) and runner up (ZGC) are performance features. And given this section had the most performance features, maybe it was also unsurprising that the ultimate winner (Virtual Threads) came from this section.

Now on to all the usual newsletter list of links, tips, tools, news and talks, and as usual I've extracted all the tips into this month's tips page.

A note from this newsletter's sponsor

News

Java performance tuning related news

• UUIDs are not incremented sortably, ie each new UUID is random. This causes massive inefficiencies for B-trees (the usual structure for indexes) if used as primary keys. Better options are ULIDs, KSUIDs, UUIDv7, Snowflake IDs
• Spring Boot Performance: Avoid Default Config Pitfalls
• Some gotchas showing how hard it is to write thread-safe code, even for experts. Advice is to use the common thread-safe structures like ConcurrentHashMap where possible

Tools

Java performance tuning related tools

• JDK Mission Control 9.1.1 released
• Oracle JVM Diagnostics (JVMD) always-on, low-overhead monitoring
• Troubleshooting Assistant leveraging GenAI

Articles

• Performance Best Practise No. 1: Optimize Database Operations (Ondro Mihalyi/foojay.io)
• Java 21 -> 25: Performance and Runtime Enhancements (Billy Korando/Inside Java)
• ZGC - Paving the GC On-Ramp (Erik Osterlund/JavaOne)

Jack Shirazi

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