Author mentions scala. Both ZIO[1] and Cats-Effect[2] provide fibers (coroutines) over these specific threadpool designs today, without the need for Project Loom, and give the user the capability of selecting the pool type to use without explicit reference. They are unusable from Java, sadly, as the schedulers and ExecutionContexts and runtime are implicitly provided in sealed companion objects and are therefore private and inaccessible to Java code, even when compiling with ScalaThenJava. Basically, you cannot run an IO from Java code.
You can expose a method on the scala side to enter the IO world that will take your arguments and run them in the IO environment, returning a result to you, or notifying some Java class using Observer/Observable. This can, of course take Java lambdas and datatypes, thus keeping your business code in Java should you so desire. It's clunky, though, and I wish Java had easy IO primitives like Scala.
You can expose a method on the scala side to enter the IO world that will take your arguments and run them in the IO environment, returning a result to you, or notifying some Java class using Observer/Observable. This can, of course take Java lambdas and datatypes, thus keeping your business code in Java should you so desire. It's clunky, though, and I wish Java had easy IO primitives like Scala.
1. https://github.com/zio/zio
2. https://typelevel.org/cats-effect/versions