Concurrent Modification exception

Question

I have this little piece of code and it gives me the concurrent modification exception. I cannot understand why I keep getting it, even though I do not see any concurrent mo

Answer 1

From the JavaDoc: for ConcurrentModificatoinException: "it is not generally permssible for one thread to modify a Collection while another thread is iterating over it".

It simply means that if you still have an open iterator, you aren't allowed to modify the list because the iterator loop will break. Try moving ListIterator it = s.listIterator(); till after the for loop.