Inconsistent Behavior with Java 18's ScheduledExecutorService When Using Callable and Future
I've searched everywhere and can't find a clear answer... I'm working with an scenario with the `ScheduledExecutorService` in Java 18 while trying to schedule tasks that return a `Future`. The question arises when I schedule multiple tasks that utilize `Callable` but I get inconsistent results when attempting to retrieve the results from the `Future` objects. Here's a simplified version of my code: ```java import java.util.concurrent.*; public class ScheduledTaskExample { public static void main(String[] args) throws InterruptedException, ExecutionException { ScheduledExecutorService executorService = Executors.newScheduledThreadPool(2); Future<Integer> future1 = executorService.schedule(new Callable<Integer>() { @Override public Integer call() throws Exception { Thread.sleep(3000); return 1; } }, 1, TimeUnit.SECONDS); Future<Integer> future2 = executorService.schedule(new Callable<Integer>() { @Override public Integer call() throws Exception { Thread.sleep(2000); return 2; } }, 2, TimeUnit.SECONDS); // Wait for the results System.out.println(future1.get()); // Expected 1 System.out.println(future2.get()); // Expected 2 executorService.shutdown(); } } ``` What I've noticed is that sometimes, when I call `future1.get()`, it returns `null`, even though I expect it to return `1`. Additionally, the scheduling seems unpredictable; occasionally, the results are returned in the wrong order or not at all. I've tried increasing the delay and changing the thread pool size, but the scenario continues. I suspect this might have something to do with how the `ScheduledExecutorService` handles task execution and completion. Is there a specific configuration or best practice for using `Callable` with `ScheduledExecutorService` that I might be missing? Has anyone else faced similar issues with version 18? Any insights would be greatly appreciated! My development environment is Windows. Any help would be greatly appreciated!