#project-leyden

#project-leyden

Nine of these features are focused on performance and runtime. Seven of these, Scoped Values, Key Derivation Function API, Module Import Declarations, Compact Source Files and Instance Main Methods, Flexible Constructor Bodies, Compact Object Headers and Generational Shenandoh, are finalized after having evolved from their respective incubations and previews with the exception of the latter two that were experimental features in JDK 24.

One of Java's longest-standing pain points is slow startup and warmup times. This is finally being addressed at the platform level in JDK 25 through enhancements tied to Project Leyden. The introduction of ahead-of-time (AOT) method profiling and improved command-line ergonomics represents meaningful progress, especially for cloud-native and microservices-based architectures where fast cold starts and elastic scaling are critical.

Build 26-leydenpremain+1 of Project Leyden early-access builds, a pre-main prototype, was made available to the Java community this past week and is based on an incomplete version of JDK 26. This build features " prototype improvements to the startup time, time to peak performance, and footprint of Java programs." Including the upcoming release of JDK 25, three JEPs, namely: JEP 483, Ahead-of-Time Class Loading & Linking; JEP 514, Ahead-of-Time Command-Line Ergonomics; and JEP 515, Ahead-of-Time Method Profiling, have been delivered by Project Leyden.