Question

I was wondering what the performance impact would be when using ArrayList.ListIterator(int index – 1), then it.next() in contrast to using ArrayList.get(int index)?

Answer 1

Why look at the implementations…

1: List.listIterator(int)

public ListIterator<E> listIterator(final int index) {
if (index<0 || index>size())
  throw new IndexOutOfBoundsException("Index: "+index);

return new ListItr(index);
}

with

private class ListItr extends Itr implements ListIterator<E> {
ListItr(int index) {
    cursor = index;
}

// [...]

and

public E next() {
        checkForComodification();
    try {
    E next = get(cursor);
    lastRet = cursor++;
    return next;
    } catch (IndexOutOfBoundsException e) {
    checkForComodification();
    throw new NoSuchElementException();
    }
}

2: List.get(int)

public E get(int index) {
RangeCheck(index);

return (E) elementData[index];
}

Should be quite obvious, which one is faster. For details about performance impacts, I will have to agree with Mike. Profile it. Whatever the reason is, you’d like to use such a distinct access method just to access one item (?)