java - Element removing while collection iterating -

i'm wondering going on behind scene when i'm executing following peace of code:

    list<object> list = new arraylist<object>();     fillthelist(); // filling list 10 objects     int count = 0;     (object o : list) {         count++;         if (count == 5) {             list.remove(count);         }         o.tostring();      } 

once element removed i'm getting concurrentmodificationexception exception.

i don't understand why after 1 of elements removing impossible take next 1 available in collection , proceed cycle.

get iterator instead of using iterator in for loop:

int count = 0;  for(final iterator iterator = list.iterator(); iterator.hasnext();) {     final object o = iterator.next();      if (++count == 5) {         iterator.remove();     }      o.tostring(); } 

edit: reason why concurrentmodificationexception because for loop using different iterator created before modification being made list.remove() , iterator has state inside.