Why it takes 3000 commits to bring Valhalla's value objects to the JDK

After years of rounding off a square peg to fit into Java's mainline, JEP 401's value objects are coming to OpenJDK in its first preview. It is a single keyword change, you don't even need to recompile your libraries, yet there's so much happening. What you can learn here:

• What value objects are, why and how you want to use them
• What value objects do for the Java Virtual Machine, and therefore your code
• Where Is OpenJDK going with this: "healing the rift" between objects and primitives

There will be some project history, concerning peak Valhalla prototype performance, and how all the dangerous bits were smoothed off to make it usable. There will be some JVM engineering details on implementation and a peek at some wild and crazy ideas for the future, hoping to be a few thesis papers in the coming months. The audience should come away with an understanding that, whilst we don't quite yet have `List`, there is a path to get there, which you will see with JEP 401.

In the meantime, JEP 401 Value Objects, holds plenty of subtle language features and interactions with the JVM to help your code be better from a safety and clarity point of view and also some performance wins along the way, with the promise of more to come...