| Corretto 25 Adds Ahead-Of-Time-Caching Support |
| Written by Kay Ewbank | |||
| Thursday, 25 September 2025 | |||
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Amazon Corretto 25, a Long Term Support (LTS) version, is now generally available. This release brings Corretto into line with JDK 25 with support for compact object headers, ahead-of-time-caching support, and CPU‑time sampling, cooperative sampling and method‑trace events for low‑overhead production profiling in JDK Flight Recorder. Amazon Corretto ia a no-cost, multiplatform, production-ready distribution of OpenJDK that is the default OpenJDK distribution on Amazon Linux and Amazon services that make use of Linux.
While Corretto is OpenJDK equivalent, it includes Amazon-developed patches derived from needs identified at Amazon, including security fixes, performance enhancements, and garbage collection scheduling as well as enhanced monitoring, reporting, and thread management. Amazon makes these patches generally available to the main OpenJDK distribution, so customers can avoid being tied-in when choosing Corretto. The improvements to this release all derive from OpenJDK 25, and start with the inclusion of Compact Object Headers, which are designed to lower heap memory usage by shrinking object headers from 96-128 bits down to 64 bits. This version also includes support for Ahead-of-Time (AOT) caching. This is designed to improve cold-start and warm-up time by reusing pre-parsed pre-linked classes and compilation profiles between training and production runs. There are a number of improvements to the language to bring Corretto into line with the latest standard, including support for primitive types in patterns, flexible constructors, module‑wide imports, compact source files, scoped values for thread-local variables, and stable values for immutable data. The generational mode of the Shenandoah garbage collector has been changed from an experimental to a production feature in this release. While the default garbage collection mode continues to be single generation, generational collection is now fully supported. Generational GC relies on the hypothesis that most objects die young, and garbage collection cycles concentrate on dealing with young and therefore mostly dead objects. The generational enhancement of the Shenandoah garbage collector separates the Java heap into two generations, and focuses on the young generation, i.e., the one in which allocations by the mutator occur and where ephemeral objects can be reclaimed with reduced effort. JDK Flight Recorder has been improved with support for CPU‑time sampling, cooperative sampling and method‑trace events for low‑overhead production profiling. This release also incudes a new Vector API that has been developed to provide computations that compile to optimal vector instructions on supported CPUs. Finally, Virtual Thread pinning has been improved for better scalability. Corretto 25 is available now. More InformationRelated ArticlesAmazon Corretto 18 Released - Why Go For It? Amazon Releases Corretto - OpenJDK Distribution Making GraalVM-Based Executables Easy Microsoft Jumps on the OpenJDK Bandwagon To be informed about new articles on I Programmer, sign up for our weekly newsletter, subscribe to the RSS feed and follow us on Twitter, Facebook or Linkedin. 
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