first of all, let's be clear: ArrayList traverses faster with for loops than iterator iterators, and LinkedList traverses faster with iterator iterators than for loops.
as to why Iterator saves time than traversing the linked list sequentially , my understanding is that because arrayList is based on arrays and the subscript is clear, get (i) is very efficient when using for loops;
while linkedList based on linked list, get (i) complexity is O (n), plus the number of loops is O (n ^ 2), but using iterator.next () does not need subscript, only the complexity of the loop can be counted