Question

Is it advisable not to use iterator.hasNext() in looping over an iterator?

For example I would like to set value obj to each element of a list. I could use the following code or make it more readable by using hasNext() in a loop.

int size = list.size();
ListIterator<? super T> itr = list.listIterator();
for (int i=0; i<size; i++) {
     itr.next();
     itr.set(obj);
}

Instead of these lines I could write my code like the following.

for (ListIterator<? super T> itr = list.listIterator(); itr.hasNext(); ) {
    itr.next();
    itr.set(obj);
}

Answer 1

Is it advisable not to use iterator.hasNext() in looping over an iterator?

Um, no. hasNext is the standard way you iterate with an iterator. That’s what the enhanced-for statement does behind the scenes for an iterable, for example.

Having said that, your code is already ListIterator-specific, as you’re using ListIterator.set – so your second block of code won’t actually compile at the moment. Even if it did, it wouldn’t work, as you still need to call next(). This would work though:

for (ListIterator<? super T> itr = list.listIterator(); itr.hasNext(); ) {
    itr.next();
    itr.set(obj);
}