Java 17 Optional Handling in Custom Method Returning Stream - Unexpected Empty Result
I'm a bit lost with I've been banging my head against this for hours. I'm working through a tutorial and Hey everyone, I'm running into an issue that's driving me crazy... I'm working with an scenario with a method in my Java 17 application where I'm using `Optional` in combination with `Stream` to process a list of items. The method is supposed to filter out certain elements and return a `Stream` of filtered results, but I'm consistently getting an empty result when it shouldn't be. Here's a simplified version of my code: ```java import java.util.List; import java.util.Optional; import java.util.stream.Collectors; import java.util.stream.Stream; public class ItemProcessor { public static void main(String[] args) { List<String> items = List.of("apple", "banana", "cherry", "date"); Stream<String> result = filterItems(Optional.ofNullable(items)); result.forEach(System.out::println); } public static Stream<String> filterItems(Optional<List<String>> optionalItems) { return optionalItems.stream() .flatMap(List::stream) .filter(item -> item.startsWith("a")); } } ``` When I run this code, I expect to see "apple" printed, but it outputs nothing. I've already verified that the list contains items starting with "a", and I even checked that the `optionalItems` is not empty. The scenario seems to stem from the way I'm using `Optional` and `Stream`. I've tried changing `optionalItems.stream()` to `optionalItems.isPresent() ? optionalItems.get().stream() : Stream.empty()`, but it feels unnecessarily verbose and doesn't seem to solve the question. I also considered that using `flatMap` might be contributing to the scenario, but I need to figure out how to avoid that while keeping the functionality intact. Is there a more idiomatic way to handle this in Java 17? Any help to get this working correctly would be greatly appreciated! I'm working on a web app that needs to handle this. Thanks in advance! Any ideas what could be causing this? Is this even possible? I'm working on a CLI tool that needs to handle this. Any advice would be much appreciated. I'm on Linux using the latest version of Java. What's the correct way to implement this?