Clarification about the following API ReentranReadWriteLock

Question

Directly from this API:

When constructed as fair, threads contend for entry using an approximately arrival-order policy. When the currently held lock is released either the longest-waiting single writer thread will be assigned the write lock, or if there is a group of reader threads waiting longer than all waiting writer threads, that group will be assigned the read lock.

It compares a single writing thread to a group of reading threads. What if there were only one waiting thread instead of a group of thread as the API specifies.. Would it change anything or it refers both to individual threads and group of threads?

Thanks in advance.

Answer 1

I'm 95% certain that "group" in this case can be read as "one or more". It should be easy enough to write a test for this. Harder but also possible is to crack open the java source and see what it's doing.

The idea here is you can give the lock to 1 writer or 1+ readers at the same time. It's just trying to say that if there are multiple readers waiting before the next writer, they all get the lock at the same time. This is safe because they're just reading.