👀 Views: 54 💬 Answers: 1 📅 Created: 2025-06-08

java concurrency completablefuture concurrenthashmap Java

Does anyone know how to Hey everyone, I'm running into an issue that's driving me crazy... After trying multiple solutions online, I still can't figure this out... I'm experiencing unexpected behavior when using `CompletableFuture` with a shared `ConcurrentHashMap` in my Java 17 application. When I try to update the map using multiple asynchronous tasks, the resulting values sometimes seem to be inconsistent or missing. Here's a simplified version of what I've implemented: ```java import java.util.concurrent.CompletableFuture; import java.util.concurrent.ConcurrentHashMap; public class MapUpdater { private final ConcurrentHashMap<Integer, String> map = new ConcurrentHashMap<>(); public void updateMap() { CompletableFuture<Void> future1 = CompletableFuture.runAsync(() -> { for (int i = 0; i < 5; i++) { map.put(i, "Value " + i); } }); CompletableFuture<Void> future2 = CompletableFuture.runAsync(() -> { for (int i = 5; i < 10; i++) { map.put(i, "Value " + i); } }); CompletableFuture<Void> combinedFuture = CompletableFuture.allOf(future1, future2); combinedFuture.join(); // Wait for all updates to complete // Print map to see the result System.out.println(map); } public static void main(String[] args) { new MapUpdater().updateMap(); } } ``` I expected the final output to contain all keys from 0 to 9 with their corresponding values. However, sometimes the output only shows values for keys 0 to 4 or 5 to 9, and other times I get missing keys altogether. I've confirmed that the tasks are running in parallel, but I suspect there might be a race condition or issue with how the map is being updated. I checked the documentation for `ConcurrentHashMap`, and I believe I'm using it correctly. I've tried adding synchronization around the updates, but that led to performance issues. Is there a better way to manage updates to the shared map in this scenario? Any insights on best practices or potential pitfalls would be greatly appreciated! I'm working on a application that needs to handle this. Thanks in advance! I'd really appreciate any guidance on this. I'm working on a service that needs to handle this. For context: I'm using Java on Ubuntu. Has anyone else encountered this? I'm working in a Linux environment. My team is using Java for this application. Has anyone else encountered this?