Avoiding ConcurrentModificationException when removing from a collection in a loop

Java's ConcurrentModificationException arises when iterating and modifying a collection concurrently. Avoid this using an Iterator's remove() method or copying to a new list.

Method 1: Using Iterator

List<String> list = new ArrayList<>(Arrays.asList("a", "b", "c"));
Iterator<String> iterator = list.iterator();
while (iterator.hasNext()) {
    String item = iterator.next();
    if (item.equals("b")) {
        iterator.remove();
    }
}

Method 2: Copying to a new list (for simpler logic)

List<String> list = new ArrayList<>(Arrays.asList("a", "b", "c"));
List<String> newList = new ArrayList<>();
for (String item : list) {
    if (!item.equals("b")) {
        newList.add(item);
    }
}
list = newList; //Replace old list

Method 3: Using streams (Java 8+) for conciseness:

List<String> list = new ArrayList<>(Arrays.asList("a", "b", "c"));
list.removeIf(item -> item.equals("b"));

Spring Boot Context: These methods apply equally to Spring Boot applications. The exception isn't specific to Spring. Choose the method best suited to your code's readability and performance needs. Using an Iterator is generally preferred for efficiency when removing many items. Streams offer conciseness but might be less performant for massive lists. Copying is simplest for small lists and straightforward logic. Remember to handle potential NullPointerExceptions if your list might contain null values.