java.util.ConcurrentModificationException & iteration?

Question

I\'m so very new to Arraylists & iterators & this is the first time I got this exception. I have an ArrayList u & I\'d like to do the following algorithm:

Answer 1

how exactly i must put the while(iter.hasNext())

You can use iterator as below:

Iterator iter = u.iterator();
while(iter.hasNext())
{
  Character c = iter.next();
  .....
}

Initialize your list with generics: List u = new ArrayList();

Hint: use iter.remove(), iter.add() wherever applicable instead of u.remove() and u.add().

You need to start here: http://www.tutorialspoint.com/java/java_using_iterator.htm