How to Avoid ConcurrentModificationException When Removing Elements from an ArrayList?

How to Overcome ConcurrentModificationException When Traversing and Removing Elements from an ArrayList

Iterating over an ArrayList while concurrently removing elements can trigger the infamous java.util.ConcurrentModificationException. To address this issue, there are several best practices to consider.

One approach is to create a separate list of elements you wish to remove. During loop iteration, add these elements to the secondary list, and once the iteration concludes, call the originalList.removeAll(valuesToRemove) method.

Alternatively, you can utilize the remove() method directly on the iterator. Note that this technique requires you to steer clear of the enhanced for loop. For instance, to eliminate strings exceeding a length of 5 from a list:

List<String> list = new ArrayList<String>();

for (Iterator<String> iterator = list.iterator(); iterator.hasNext(); ) {
    String value = iterator.next();
    if (value.length() > 5) {
        iterator.remove();
    }
}

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