> Before we pop the champagne, though: this is preview, disabled by default, and, as Brian Goetz was quick to cool everyone down, “only the first part of Valhalla.” Goetz added a great observation that the “they’ll never ship it” crowd will now smoothly switch over to “but they didn’t ship the most important part” (and a joke has been going around the community for years that we’ll sooner end up in Valhalla ourselves, the Norse-afterlife one, than the project ships).
I don’t know if this is fair way to try to disarm your critics. The only thing that’s remained after this decade is the slogan so it’s a real ship of Theseus question if Valhalla has shipped since what’s delivered doesn’t achieve it. Congrats on the accomplishment, but from looking at what ended up, I’m not sure it’s a huge improvement.
> The trouble is that this optimization is unpredictable and fragile.
Is this describing escape analysis or value classes? Because the list of exclusions where this does anything is so large and the conversion to a heap type under the hood is so transparent and opaque, I think it can describe this technique as well.
Also, the whole “works like an int” motto is violated - int is never null, int-> integer boxing is explicit and well understood.
> In the new model, the wrapper classes themselves become value classes (when preview is on, Integer, Long, Double, and company lose their identity
Oh neat, they sidestep that by changing the definition of an int. I’m sure it’ll be trivial to turn this on in the wild on code that may be relying on identity for boxed numerics. I think this alone shows this project can’t ever be turned on by default and now we’ll have a decade of two Java languages (one with value types and one without) as they try to convince everyone to migrate and then just turn it on (ie python3).
So much opportunity squandered and dismissing critics as always having something to complain about is a neat way to sidestep legitimate criticism that this approach is not going to work out for Java.