The Holy Grail of Java Performance

Project Leyden aims to improve Java startup time, time to peak performance, and memory footprint. The core idea, proposed by Mark Reinhold, is to generalize how Java shifts computation across phases (compile time, link time, archive time, run time) using a new concept called condensers. A condenser is an optional transformation phase that takes a code artifact, performs some computation early, and outputs an optimized artifact. Condensation must be meaning-preserving, composable, and selectable by developers. To enable powerful optimizations while handling Java's dynamic nature, the Java Platform Specification would be extended with a list of permitted constraints (e.g., prohibiting class redefinition, run-time subclassing, or reflection). Combining these constraints could eventually enable native image generation within Java spec bounds, representing the holy grail of Java performance.