Unexpected NullPointerException When Using CompletableFuture with Custom Executor in Java 17
I'm testing a new approach and I'm building a feature where I'm experiencing a `NullPointerException` when trying to use `CompletableFuture` with a custom executor in Java 17. My goal is to run multiple tasks concurrently by submitting them to a custom thread pool, but I keep running into issues. Here’s a simplified version of my code: ```java import java.util.concurrent.CompletableFuture; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class CustomExecutorExample { public static void main(String[] args) { ExecutorService executor = Executors.newFixedThreadPool(3); CompletableFuture<Void> future = CompletableFuture.runAsync(() -> { // Simulate some processing processTask(); }, executor); future.join(); executor.shutdown(); } private static void processTask() { String result = getResult(); // This line throws NullPointerException System.out.println(result); } private static String getResult() { // Simulating some logic that can return null return null; } } ``` When I run this code, I receive a `NullPointerException` at the line where `getResult()` is called inside `processTask()`. I expected that since I'm handling the tasks with `CompletableFuture`, it would gracefully manage any return values or exceptions. I've also tried adding exception handling inside the `runAsync` method, but the behavior still surfaces when the `processTask()` method is invoked. I’m unsure if this is due to the nature of `CompletableFuture` or my custom executor setup. I've seen examples where exceptions are handled within the `CompletableFuture`, and the behavior seems to differ based on how the tasks are defined. How can I prevent this `NullPointerException` from disrupting my workflow? Is there a better way to handle potential null values in a concurrent setting without compromising the task's execution flow? Any advice would be greatly appreciated! Thanks for taking the time to read this!