Comment by orthoxerox

As I understand it, this is anyway an extremely limited perf enhancement - for any class whose data size isn't guaranteed to be atomically writable on your CPU, after including the nullability overhead, it doesn't do anything, basically. On a CPU where 64 bits is the max guaranteed atomic read/write, even Point[] will not get optimized, since you need at least 65 bits of memory for a point value (since it has two 32 bit int fields, and it needs an extra bit to specify if it's null or not - so in practice it will take up 72 bits at the very least, possibly more with alignment requirements). But even after fixing this, if you have 3D points or if you need 64bit coordinates, your value type 3DPoints will still be individually heap allocated and your 3DPoint[] will store pointers to them, just like today, on most processors.

Given that the JVM could already do escape analysis and allocate regular classes on the stack in certain scenarios, it's very unclear what benefit, if any, this will bring for normal processors for anything except the base wrapper types - even after implementing generic support and nullability for value types in a future JVM.

Yup. That's a big disappointment they could not cram universal generics faster. But I get the problem - they have to preserve backwards compatibility. I can take 30 y.o. Java 1.0 JAR and run it on Java 27 and it will work.