[coldtea]

I also have the feeling that's only pjmlp and maybe 100 enterprises around the world that do use some features like these!

You always seem to mention them (class sharing, Java AOT compilers, etc), but nobody (for values of somebody < enough) seems to be actually using them :-)

[pjmlp]

When one does enterprise computing those features are available to anyone that cares.

It is not my fault many developers don't care about their tooling, and settle for worse is better. :)

[coldtea]

So, that's my question then: are those features really mature and available for using in production.

Or is it like some half-done features with several caveats and/or some companies with this or that compiler extension (like Java AOT), that might or might not work well, not have good documentation, or any kind of support, and that some cavalier daredevils opt to use?

I mean, I'm not 100% convinced whether it's devs don't caring, or the tools being niche and "use at your own peril", the reason for that lack of adoption.

GraalVM, for example, probably still has some rough edges, and that's an official Oracle tool.

In your experience which are the maturest alternative Java deployment tools/compilers/options?

[pjmlp]

GraalVM is mature enough to power Twitter.

AOT compilers for Java exist in production since around 2000, basically all commercial JVMs supported it, specifically those targeted for embedded deployment.

AppCDS in Hotspot is nothing new, basically just like Flight Recorder, proven components from BEA J/Rockit JVM acquired by Oracle, which they eventually decided to make available on Hotspot.

Likewise OpenJ9 AOT and JIT caches, have years of production testing, from IBM J9 deployments in WebSphere Realtime JVM (now discontinued), IBM mainframes, Aix and Linux.

PTC and Sonic have been used for years in military deployments, and factory automation scenarios.

Aicas focus mainly in embedded scenarios.

Excelsior JET was quite good, but for whatever reason they went bankrupt.

Android Runtime, although not Java, has been AOTing since Android 5, starting with Android 7 evolved into a mix of interpreted/JIT/AOT with PGO from JIT, in Android 10 gained the ability to upload PGO profiles to the store so that devices can AOT right away.