RFC: Adding ConcurrentModificationException for HashMap.computeIfAbsent(), and JDK-8071667

[Ben Manes]

I'd recommend that the exception thrown should be an IllegalStateException. This is documented in ConcurrentHashMap's computeIfAbsent as,

* @throws IllegalStateException if the computation detectably
*         attempts a recursive update to this map that would

*         otherwise never complete

The detection logic is in Doug's repository to be merged in for JDK-8062841.

It is also unexpected to have a concurrent data structure throw a ConcurrentModificationException, which is why I believe that IllegalStateException was chosen for ConcurrentHashMap.