In Java the layout of objects is abstracted away from the application, leaving Java inherently challenged by concerns such as interoperation with native data structures, the dense packing of Java objects and cache conflicts and false sharing.
With PackedObjects, there is a proposal for a new explicit object model that enables direct binding of native data structures, dense packing of Java objects to improve the performance of operations such as serialization, and precise object layout to allow for finer-grained control over locality and the development of a high-performance concurrent library.
https://www.youtube.com/watch?v=MkoM__29ZnY