Your question is not correct,Hash Map iterator are Fail-Fast.
Fail fast and Fail safe comes in to picture when we talk about concurrent access.
Fail fast iterator while iterating through collection throws concurrent modification exception when it finds out that collection is being modified by some other thread,so iterator fails quickly and cleanly.
Fail safe iterator do the copy of collection and iterate through it so no changes get reflected to original data so no concurrent modification exception. ConcurrentHash Map iterator are fail safe.