フリー問題

問題文

Which statement correctly describes virtual threads as they were finalized in Java 21?

選択肢

1. They can only be created through the scope class that groups related subtasks and waits for all of them to finish.
2. They run without any stack, so a task which recurses deeply must be rewritten while it is ported.
3. They map one to one onto operating system threads, so creating a large number of them consumes the same amount of memory as before.
4. They are scheduled by the runtime onto a small pool of carrier threads, so a blocking call usually releases the carrier for other work.