In terms of memory utilization which is better to iterate through a LIST?

Question

For Loop or Iterator Class.?????

Answer 1

1. For loop and Iterator are not mutually exclusive. One common way to iterate before the foreach loop introduced in 1.5 (my preferred way) was like so:
for (Iterator iter = list.iterator(); iter.hasNext();) {
  Object obj = iter.next();
}2. By "for loop" I assume you mean "using get()". NEVER iterate using get(). It will work fine on ArrayList, but will be crappy slow on LinkedList, and doesn't exist on Set or Collection. Using an Iterator (or foreach, which is syntactic sugar for an Iterator) means you'll get proper and consistent behavior on any colleciton.
3. The memory usage will not be any different, or will be ridiculously insignificant. This kind of microoptimization without hardcore profiling numbers is a good way to gain a tiny, meaningless bit in one area at a much larger cost in another area.
Just use a foreach loop, or in cases where you need to modify the collection under iteration, an explicit Iterator or ListIterator.