👀 Views: 0 💬 Answers: 1 📅 Created: 2025-08-28

java completablefuture exception-handling Java

I'm dealing with I'm building a feature where I'm maintaining legacy code that I'm experiencing unexpected behavior when using `CompletableFuture` in Java 11 to chain multiple asynchronous tasks... I have a pipeline where the first task fetches data from an API, and the second task processes that data. However, if the first task throws an exception, the second task is still executing instead of being skipped. Here's a simplified version of my code: ```java import java.util.concurrent.CompletableFuture; import java.util.concurrent.ExecutionException; public class CompletableFutureExample { public static void main(String[] args) { CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> { // Simulating an API call that throws an exception throw new RuntimeException("API call failed"); }).thenApply(result -> { // This should not be executed if the previous call failed return "Processed: " + result; }); try { // This will throw ExecutionException due to the failure in the first task String finalResult = future.get(); System.out.println(finalResult); } catch (ExecutionException e) { System.out.println(e.getMessage()); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } ``` I expected the second task (`thenApply`) not to run if the first task fails, but it seems to be executing regardless. I also tried using `exceptionally` to handle exceptions, but it doesn't change the flow of execution for the chained tasks. Here's what I tried: ```java CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> { throw new RuntimeException("API call failed"); }).exceptionally(ex -> { System.out.println("Handled exception: " + ex.getMessage()); return "Fallback response"; }).thenApply(result -> { return "Processed: " + result; }); ``` In this case, my output is `Processed: Fallback response`, but I want to ensure that if the first task fails, the second should not be processed at all. How can I achieve that while still being able to handle the exception properly? I'm working on a application that needs to handle this. Could someone point me to the right documentation? I'm working with Java in a Docker container on Windows 10. I'd be grateful for any help.