The rest of the stuff, incl. I/O is actually on the trivial side - threads do require planning. This is what I meant by being a 'toy' project, threads (and JMM) would be impossible to bolt in later on.

The reason you're being downvoted is you keep dismissing this as a "toy" project, and pointing out that it would be hard to make a real project.

But, as the previous commenter attempted to point out to you this project is a *self-described* toy project.

On the very page that is linked, the author of the JVM specifically says:

"I want to stress that this is a toy JVM, built for learning purposes and not a serious implementation."

Thus, absolutely no one disagrees that its a toy JVM. They just want you to stop being dismissive of someone's toy project by repeatedly pointing out its a toy project and not a "not a thing"

Right, just because something is a "toy" doesn't mean it's not still impressive. If someone implemented a "toy" database that could parse and execute SQL queries, distribute data across nodes, etc., you would probably not want to use that in production, but it's still a very impressive project for a single person to pull off, even if it's riddled with bugs. Getting a very complex system to "just barely functional" is still a huge achievement and very cool!

Being impressing or otherwise is very subjective.

SQL (ACID) over multiple non-cache-coherent nodes is extremely difficult to pull with regards to consistency, though.

> SQL (ACID) over multiple non-cache-coherent nodes is extremely difficult to pull with regards to consistency, though.

Thats... why it's a toy! I'm really not sure what you're missing here.

you must be fun to work with

I've pointed the only part that makes it a toy project is the lack of Threading support, the rest is not hard to add. So the items in list of things missing after 'toy' thing should have totally different weights (with Threads being the added to the last).

You're still missing the point—it was always intended to be a toy project, and the author has explicitly declared that they are completely done with it and won't be doing any more work. What does it matter how they sort the list of missing items? It's not a todo list in need of prioritization, it's just an "FYI, these are some of the things I never got to".