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Iterator allows to remove elements during iteration

With a for each loop you can iterate easily through a collection but you cannot remove elements during iteration.
List<String> list = new ArrayList<String>();
list.add("Max");
list.add("bob");
list.add("Alex");

// for each loop:
// execution this loop ends with a
// java.util.ConcurrentModificationException
for (String element : list) {
   list.remove(element);
}
A java.util.Iterator is a suitable solution for the above situation, because it allows you to remove elements from a collection during iteration.
Iterator<String> iterator = list.iterator(); 

while (iterator.hasNext()) {
   iterator.next()); 
   iterator.remove();
}
Iterator interface has three methods:
boolean hasNext()
E next()
void remove()
and allows for iteration in a one direction. If you want to iterate through a list in both directions you should use a ListIterator (implements Iterator) which has additional methods:
boolean hasPrevious() 
E previous()
int previousIndex() 
int nextIndex()
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