Java 17: Inconsistent Behavior with ScheduledExecutorService and Callable Returning Null
I'm building a feature where I'm reviewing some code and I'm getting frustrated with I've hit a wall trying to I'm working with an scenario with `ScheduledExecutorService` in Java 17 where the `Callable` tasks sometimes return `null`, leading to unexpected behavior in my application scheduling logic... I have implemented a scheduled task that fetches data every minute, but occasionally the result is `null`, which I wasn't expecting. Here’s a simplified version of my code: ```java import java.util.concurrent.*; public class ScheduledTaskExample { private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1); public void start() { Runnable task = () -> { try { String result = scheduler.schedule(this::fetchData, 1, TimeUnit.MINUTES).get(); if (result == null) { System.out.println("Received null result. Retrying..."); } else { System.out.println("Data fetched: " + result); } } catch (InterruptedException | ExecutionException e) { System.err.println("behavior fetching data: " + e.getMessage()); } }; scheduler.scheduleAtFixedRate(task, 0, 1, TimeUnit.MINUTES); } private String fetchData() { // Simulating a data fetch, sometimes returning null if (Math.random() < 0.5) { return null; // Simulate no data available } return "Data at " + System.currentTimeMillis(); } public static void main(String[] args) { new ScheduledTaskExample().start(); } } ``` In the code above, the `fetchData` method randomly returns `null` to simulate cases where no data is available. When this happens, I'm expecting to see a retry message, but sometimes the task fails to execute again, and I receive an `ExecutionException` instead. I've tried wrapping the `schedule` call in a try-catch block, but it doesn’t seem to affect the intermittent behavior. I’ve also verified that the `ScheduledExecutorService` is not shutting down unexpectedly and that the main application thread remains active. Is there a better way to handle scenarios like this where tasks might return `null`, or is there something in my implementation that could lead to these inconsistencies? Any insights would be greatly appreciated! The project is a mobile app built with Java. Any help would be greatly appreciated! Thanks for your help in advance! This is part of a larger CLI tool I'm building. This is happening in both development and production on Ubuntu 20.04. Thanks for your help in advance!