ConcurrentModificationException

I got this exception today during operating on a List. It seems to me a rare exception. 

I had to remove few items from a list. I was removing one by one with the List.remove(object). Then got this exception. I was looking for a quick solution. Without being bothered about concurrency. I just made another list of elements which has to be removed from my main list. And finally called the List.removeAll(Collection). It worked nice. 

Code is like this.

List myMainList;

iterate over myMainList

if(certain conditions)

elementsToBeReoved.add(theElement);

myMainList.removeAll(elementsToBeRemoved);