fold left java

gistfile.java

public static <A, B> B foldLeft(Stream<A> iterable, B identity, BiFunction<B, A, B> bf) {
    return foldLeft(iterable.iterator(), identity, bf);
}

public static <A, B> B foldLeft(Iterable<A> iterable, B identity, BiFunction<B, A, B> bf) {
    return foldLeft(iterable.iterator(), identity, bf);
}

public static <A, B> B foldLeft(Iterator<A> iterator, B identity, BiFunction<B, A, B> bf) {
    B result = identity;
    while(iterator.hasNext()) {
        A next = iterator.next();
        result = bf.apply(result, next);
    }
    return result;
}