Java ConcurrentModificationException: Causes, Solutions, and Best Practices

The "java.util.ConcurrentModificationException" is an exception that occurs when a collection is modified while it is being iterated over using an iterator or a for-each loop. This exception is thrown to prevent concurrent modifications to the collection, as it can lead to unexpected behavior or inconsistencies.\n\nTo avoid this exception, you can use an iterator explicitly and call its "remove()" method to remove elements from the collection while iterating. Alternatively, you can make a copy of the collection and iterate over the copy instead of the original collection.\n\nHere is an example of how the exception can occur:\n\njava\nList<Integer> numbers = new ArrayList<>();\nnumbers.add(1);\nnumbers.add(2);\nnumbers.add(3);\n\nfor (Integer number : numbers) {\n if (number == 2) {\n numbers.remove(number); // ConcurrentModificationException occurs here\n }\n}\n\n\nIn this example, the exception occurs because we are removing an element from the "numbers" list while iterating over it using a for-each loop. To fix this, we can use an iterator and its "remove()" method:\n\njava\nList<Integer> numbers = new ArrayList<>();\nnumbers.add(1);\nnumbers.add(2);\nnumbers.add(3);\n\nIterator<Integer> iterator = numbers.iterator();\nwhile (iterator.hasNext()) {\n Integer number = iterator.next();\n if (number == 2) {\n iterator.remove(); // Remove the element using iterator's remove() method\n }\n}\n\n\nIn this updated example, we use an iterator to iterate over the "numbers" list, and when we want to remove an element, we call the iterator's "remove()" method. This avoids the ConcurrentModificationException.