Project Valhalla

Project Valhalla plans to augment the Java object model with value objects and user-defined primitives, combining the abstractions of object-oriented programming with the performance characteristics of simple primitives. These features will be complemented with changes to Java’s generics to preserve performance gains through generic APIs.

This Project is sponsored by the HotSpot Group.


Valhalla project features will be added to Java over multiple releases. This process is managed with JEPs, each of which facilitates the development and integration into the JDK of a cohesive set of changes.

Background Documents

These documents present a more holistic view of the Valhalla project’s goals and design considerations.


Prototyping for the project takes place in a public OpenJDK repository, with occasional early-access builds being published.

Interested developers are encouraged to experiment with these prototypes.

Branches in the repository include lworld (the main line of Valhalla development), master (tracking mainline OpenJDK), jep* (staging areas for the production-ready implementations of JEPs), and various others prototyping proposed features.


We welcome input from interested Java developers. Keep in mind that most theoretical ideas have been well explored over the last few years! The greatest help can be provided by those who try out concrete prototypes and can share their experiences with real-world code bases.