Is there a performance difference between a for loop and a for-each loop?

Question

What, if any, is the performance difference between the following two loops?

for (Object o: objectArrayList) {
    o.DoSomething();
}

and <

Answer 1

Well, performance impact is mostly insignificant, but isn't zero. If you look at JavaDoc of RandomAccess interface:

As a rule of thumb, a List implementation should implement this interface if, for typical instances of the class, this loop:

for (int i=0, n=list.size(); i < n; i++)
    list.get(i);

runs faster than this loop:

for (Iterator i=list.iterator(); i.hasNext();)
      i.next();

And for-each loop is using version with iterator, so for ArrayList for example, for-each loop isn't fastest.