How to Avoid java.util.ConcurrentModificationException When Removing Elements from an ArrayList During Iteration?

Handling Concurrent Modification in ArrayList Iteration

When iterating through an ArrayList and simultaneously removing elements, you can encounter a dreaded java.util.ConcurrentModificationException. To address this issue, consider the following strategies:

1. Create a Removal List

Maintain a separate list of elements to remove. During iteration, simply add elements to this list rather than removing them directly from the ArrayList. Once the iteration is complete, use the removeAll() method to remove all the accumulated elements from the original list in one go. This approach ensures that no modifications occur during iteration, avoiding the ConcurrentModificationException.

2. Use Iterator.remove()

Utilize the iterator's remove() method directly. This technique requires using the traditional for loop instead of the enhanced for loop. While iterating, if you need to remove an element, simply call remove() on the current iterator. This approach modifies the underlying list as you iterate, but it ensures consistency and eliminates concurrent modification issues.

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