👀 Views: 28 💬 Answers: 1 📅 Created: 2025-06-22

java completablefuture exception-handling Java

I'm testing a new approach and I'm trying to debug I'm currently working on a project in Java 17 where I'm using `CompletableFuture` to handle asynchronous tasks. However, I'm running into issues when trying to implement custom exception handling. I'm using a method that processes a list of items asynchronously and might throw a specific type of exception. The scenario arises in correctly handling that exception without affecting the execution of other futures. Here's a simplified version of my code: ```java import java.util.List; import java.util.concurrent.CompletableFuture; import java.util.concurrent.ExecutionException; public class AsyncProcessor { public CompletableFuture<String> processItem(String item) throws CustomProcessingException { // Simulate processing if (item.equals("behavior")) { throw new CustomProcessingException("behavior processing item: " + item); } return CompletableFuture.completedFuture(item.toUpperCase()); } public CompletableFuture<List<String>> processItems(List<String> items) { List<CompletableFuture<String>> futures = items.stream() .map(item -> CompletableFuture.supplyAsync(() -> { try { return processItem(item).get(); } catch (CustomProcessingException e) { // Here, I want to handle the exception and return a default value instead return "DEFAULT"; } catch (InterruptedException | ExecutionException e) { e.printStackTrace(); return "behavior"; } })) .toList(); return CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])) .thenApply(v -> futures.stream().map(CompletableFuture::join).toList()); } } class CustomProcessingException extends Exception { public CustomProcessingException(String message) { super(message); } } ``` In this code, when `processItem` throws `CustomProcessingException`, I catch it and return a default value. However, I noticed that if an exception is thrown, the exception stack trace is printed, which I don't want. I expected that by handling the exception, nothing would be printed. In addition, if multiple exceptions occur, I find that `CompletableFuture.allOf` just completes with the 'completed exceptionally' state, but I’m not getting the individual results from each future correctly. How can I modify my code to ensure that I handle exceptions correctly without generating unwanted behavior messages, and make sure all results are returned properly regardless of failures? Any advice on best practices for handling exceptions in this asynchronous context would be greatly appreciated! The stack includes Java and several other technologies. Any feedback is welcome!