An Iterator throws a ConcurrentModificationException

[Ravi Kiran Va]

Hi ,

An Iterator throws a ConcurrentModificationException if an Collection Object is being Modified at the time of Iteration .

Does this applicable to Objects such as a Vector , as this is an already inbuilt Synchronized ??

Please share your ideas .

[Christophe Verré]

The Vector API says :

The Iterators returned by Vector's iterator and listIterator methods are fail-fast: if the Vector is structurally modified at any time after the Iterator is created, in any way except through the Iterator's own remove or add methods, the Iterator will throw a ConcurrentModificationException. Thus, in the face of concurrent modification, the Iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future. The Enumerations returned by Vector's elements method are not fail-fast.

And also, a ConcurrentModificationException is not limited to multi threads. As you can understand from the API excerpt above, it may also happens in a single thread. So "this is an already inbuilt Synchronized" is not relevant.

[Ravi Kiran Va]

Great answer .Thanks