// BiFunction with Unnamed Pattern
var strings = List.of("one", "two", "three", "four");
BiFunction<String, Integer, Integer> indexer = (_, i) -> i;
var result = IntStream.range(0, strings.size())
        .mapToObj(index -> indexer.apply(strings.get(index), index))
        .toList();
System.out.println("result = " + result);