https://openjdk.org/projects/valhalla/design-notes/state-of-...

Project Valhalla got its start in 2014, with the goal of bringing more flexible flattened data types to JVM-based languages, in order to restore alignment between the programming model and the performance characteristics of modern hardware. (In some ways, it got started much earlier; the designers of Java wanted to include value types in the initial version of the language.)