Which is more efficient, a for-each loop, or an iterator?

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Which is the most efficient way to traverse a collection?

List<Integer>  a = new ArrayList<Integer>();
for (Integer integer : a) {
  integer.toString();
}

or

List<Integer>  a = new ArrayList<Integer>();
for (Iterator iterator = a.iterator(); iterator.hasNext();) {
   Integer integer = (Integer) iterator.next();
   integer.toString();
}

Please note, that this is not an exact duplicate of this, this, this, or this, although one of the answers to the last question comes close. The reason that this is not a dupe, is that most of these are comparing loops where you call get(i) inside the loop, rather than using the iterator.

As suggested on Meta I will be posting my answer to this question.

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