| Basis of Comparison | Fail Fast Iterator | Fail Safe Iterator |
|---|---|---|
| Operates | It operates directly on the collection itself. | It operates on a cloned copy of the collection. |
| Exception | It throws a ConcurrentModificationException in modifying the object during the iteration process. | It does not throw Exception. |
| Clone Object | No clone object is created during the iteration process. | A copy or clone object is created during the iteration process. |
| Memory utilization | It requires low memory during the process. | It requires more memory during the process. |
| Modification | It does not allow modification during iteration. | It allows modification during the iteration process. |
| Performance | It is fast. | It is slightly slower than Fail Fast. |
| Examples | HashMap, ArrayList, Vector, HashSet, etc. | CopyOnWriteArrayList, ConcurrentHashMap, etc. |
