Handling Concurrent Modification Exception in Java 11 with Streams and External Iterators
I'm trying to configure After trying multiple solutions online, I still can't figure this out... I'm facing a `ConcurrentModificationException` when trying to update a list while iterating over it using Java 11 Streams. The project involves processing a list of user records where I need to remove inactive users and also update their last activity timestamp in a second list. The issue arises because I’m modifying the list of user records while iterating through it. Here’s a simplified version of my code: ```java List<User> users = new ArrayList<>(); // Assume this list is populated List<User> inactiveUsers = new ArrayList<>(); // Populate inactiveUsers based on some criteria users.removeIf(user -> !user.isActive()); // This line throws ConcurrentModificationException users.forEach(user -> { if (!user.isActive()) { inactiveUsers.add(user); user.setLastActivity(LocalDateTime.now()); } }); ``` Despite trying to use `removeIf`, it seems to not work as expected when iterating through the list with `forEach`. I’ve read that using an external iterator might be the solution, but I'm not sure how to integrate that with my current logic. I want to maintain the process as efficient as possible without creating additional collections unnecessarily. What would be the best way to handle this scenario without running into `ConcurrentModificationException`? Are there particular design patterns or best practices I should consider? I’ve also looked into using `Iterator<User>`, but it feels cumbersome to manage the state manually. Any suggestions or code examples would be greatly appreciated! This is part of a larger service I'm building. This issue appeared after updating to Java stable. What would be the recommended way to handle this?