fill() vs. fillOptional()

    void test() {

        // Filling collections with values, similar to
        // Collections.fill();

        List<Optional<Number>> optionalList1 = new ArrayList<>();
        List<Number> list1 = new ArrayList<>();

        fillOptional(optionalList1, 1);
        fillOptional(optionalList1, 1.0);

        fill(list1, 1);
        fill(list1, 1.0);
    }

    <T> void fill(List<? super T> list, T value) {
        ListIterator<? super T> it = list.listIterator();

        while (it.hasNext()) {
            it.next();

            it.set(value);
        }
    }

    <T> void fillOptional(List<Optional<T>> list, T value) {
        ListIterator<Optional<T>> it = list.listIterator();

        while (it.hasNext()) {
            it.next();

            it.set(Optional.of(value));
        }
    }
}