Gatherers_D4.snippet

// Combining With Default Value Gatherer
static <T, R, RR> Gatherer<T, ?, RR> zip(
   Iterable<R> iterable,
   BiFunction<? super T, ? super R, ? extends RR> combiner,
   R defaultValue) {

   return Gatherer.ofSequential(
      iterable::iterator,
      (iterator, element, downstream) -> {
         if (iterator.hasNext()) {
            var result = combiner.apply(element, iterator.next());
            return downstream.push(result);
         } else {
            var result = combiner.apply(element, defaultValue);
            return downstream.push(result);
         }
      }
   );
}

var strings = List.of("one", "two", "three");
var ints = List.of(1, 2, 3, 4, 5);

var result = ints.stream().gather(zip(strings, (i, s) -> i + " -> " + s, "NO_VALUE")).toList();
System.out.println("result = " + result);