[cyberax]

There are many other implementations, although in less popular languages.

The trick is to include the green threads from the start, so there are no libraries that depend on real threading. That's why Go and Erlang are so successful.

[kelnos]

The funny thing is that Java did have green threads back in v1.1, but they were dropped in v1.3.

That doesn't invalidate your point; more than 20 years of Java practice has focused on making things work well for platform threads.

[andrewf]

I think Solaris moved from green threads to pure kernel threads at the same time (https://docs.oracle.com/cd/E19253-01/816-5137/mtintro-75924/... says Solaris 9 was the transition point).