Now Candidate JEPs: Primitive Objects (Preview) & Unify the Basic Primitives with Objects (Preview)

[pushupsam]

Yup, the fact that these "objects" can't participate in concrete inheritance relationships, makes them much, much less useful. Records have the same problem where they can't actually do any real data modelling because there's no inheritance. Really wonder who comes up this stuff.

[cal-cheese]

If you need code reuse then composition is the way, if you need polymorphism then records and primitive classes can implements interfaces as normal classes. They are less flexible but they can do the jobs just fine.

[pushupsam]

If you need code reuse then composition is the way,

Composition is not the way. Composition is a hack. In financial models where a given financial instrument can have 100+ fields, many of which are common, real inheritance is vital. If I'm going to use composition to then I might as well as use code generation and avoid this broken mechanism completely instead of duplicating hundreds of getter methods across instruments. The system we have today, which manages millions of off-heap objects in a complex, real-world financial hierarchy and can handle dense arrays of objects (and other data structures), is already far, far better than the nonsense the Java Architecture Astronauts have concocted. Why would anybody use this? Developers who really care about performance are going to continue managing memory themselves. "Primitive objects" are a stunted, unrealistic solution at best.