👀 Views: 14 💬 Answers: 1 📅 Created: 2025-06-12

java concurrency streams

Hey everyone, I'm running into an issue that's driving me crazy... I'm facing a `ConcurrentModificationException` when trying to filter a list using Java Streams with Java 17. The issue arises when I'm modifying the list concurrently while processing it. Here’s a simplified version of my code: ```java import java.util.ArrayList; import java.util.List; import java.util.stream.Collectors; public class StreamExample { private List<String> items = new ArrayList<>(); public StreamExample() { items.add("apple"); items.add("banana"); items.add("cherry"); } public void processItems() { // This thread modifies the list new Thread(() -> { items.add("date"); }).start(); // This tries to filter items concurrently List<String> filteredItems = items.stream() .filter(item -> !item.equals("banana")) .collect(Collectors.toList()); System.out.println(filteredItems); } public static void main(String[] args) { new StreamExample().processItems(); } } ``` When I run this code, I occasionally get a `ConcurrentModificationException`, especially when the filter operation is executed while the other thread is adding an item. I've tried using `Collections.synchronizedList(new ArrayList<>())`, but that hasn't resolved the issue. Is there a recommended way to handle concurrent modification in this scenario? Should I consider using `CopyOnWriteArrayList` or some other concurrency utility? Any advice on best practices for this situation would be greatly appreciated. For reference, this is a production CLI tool. Could someone point me to the right documentation?