Java 11: implementing ConcurrentModificationException Using CopyOnWriteArrayList in Multi-threaded Environment
I'm not sure how to approach Hey everyone, I'm running into an issue that's driving me crazy. I'm optimizing some code but I'm working with a `ConcurrentModificationException` while trying to iterate over a `CopyOnWriteArrayList` in a multi-threaded context... Initially, I thought using `CopyOnWriteArrayList` would prevent such exceptions since it's designed for concurrent modifications. However, I still encounter this scenario occasionally, especially when using a custom iterator in a loop that modifies the list concurrently. Here's a simplified version of my code: ```java import java.util.List; import java.util.concurrent.CopyOnWriteArrayList; public class Example { private final List<String> list = new CopyOnWriteArrayList<>(); public void addItem(String item) { list.add(item); } public void processItems() { for (String item : list) { // Simulate processing System.out.println(item); if (item.equals("removeMe")) { list.remove(item); // This line causes ConcurrentModificationException } } } } ``` In this example, I am trying to remove an item from the `list` while iterating over it. Although `CopyOnWriteArrayList` is meant to handle concurrent modifications safely, I'm still getting the `ConcurrentModificationException` when running this code in multiple threads. I've tried wrapping the `remove` call with a synchronized block, but that didn't resolve the scenario. For instance: ```java public synchronized void processItems() { for (String item : list) { // Processing logic if (item.equals("removeMe")) { list.remove(item); } } } ``` Even after synchronizing, I still run into issues. Am I missing something in how I manage the iterations and modifications? Should I consider using a different approach or structure for handling this situation? Any help or guidance on resolving this would be greatly appreciated! For context: I'm using Java on Windows 10. Is this even possible? I've been using Java for about a year now. Any ideas what could be causing this? What's the correct way to implement this? I recently upgraded to Java stable. What would be the recommended way to handle this?