List vs List iterator

Answer 1

Using an Iterator provides much safer access to the List from outside the defining class as you cannot accidentally override the entire List for example. You can only ever access one element at a time: the top one.

So the guideline we use is to only use the for each approach inside the defining class and whenever the List needs to be accessed from the outside an iterator has to be used. This also enforces the concept of keeping the logic of how to modify a member inside the class that contains it. All complex operations that are needed outside have to be implemented in public methods inside that class.