Getting Unexpected NullPointerException in Java Stream Pipeline with Optional Objects
I'm refactoring my project and I just started working with I'm having trouble with I tried several approaches but none seem to work....... I'm stuck on something that should probably be simple. I'm working with a frustrating scenario where my Java stream pipeline is throwing a `NullPointerException` when I try to process a list of objects that contain `Optional` fields. I'm using Java 11 and the `Stream` API to filter and transform a list of users. The user objects may have a `nickname` field that is wrapped in `Optional<String>`. I've tried using `flatMap` to handle the `Optional`, but I'm still running into issues. Here’s a simplified version of my code: ```java import java.util.List; import java.util.Optional; import java.util.stream.Collectors; class User { private final Optional<String> nickname; public User(Optional<String> nickname) { this.nickname = nickname; } public Optional<String> getNickname() { return nickname; } } public class UserProcessor { public List<String> getNicknames(List<User> users) { return users.stream() .map(User::getNickname) // This returns Optional<String> .flatMap(Optional::stream) // Attempting to convert Optional to Stream .collect(Collectors.toList()); } } ``` When I run this, I get the following behavior: ``` Exception in thread "main" java.lang.NullPointerException at UserProcessor.getNicknames(UserProcessor.java:7) at Main.main(Main.java:10) ``` I double-checked the users list to ensure it's not null, but the scenario seems to arise from some `User` objects having their `nickname` set to `null` instead of `Optional.empty()`. I thought using `Optional` would inherently prevent these nulls, but it seems like my code still has an edge case that I'm missing. Is there a best practice or a different approach I can take to avoid this scenario? Any help would be greatly appreciated! This is part of a larger application I'm building. Has anyone else encountered this? For context: I'm using Java on Windows. Is there a better approach? Has anyone dealt with something similar? I've been using Java for about a year now. Thanks for your help in advance! I'm coming from a different tech stack and learning Java. Any suggestions would be helpful.