What is the feature of using CopyOnWriteArrayList…

CopyOnWriteArrayList is a thread-safe list where modification operations (add, set, remove, etc.) create a new copy of the underlying array.

Key features:

Thread safety: All add, set, remove operations are thread-safe because they do not modify the array referenced by current readers. Instead, a new array with the changes is created, and the reference is atomically updated.
Read performance: Read operations (get, iterator, etc.) are very fast because they do not require synchronization. They work with an immutable copy of the array.
Write overhead: Write operations can be very costly, especially for large lists, because they require creating and copying the entire underlying array.
Iterators: Iterators obtained from CopyOnWriteArrayList are "snapshots" of the list's state at the moment of their creation. They do not reflect changes made to the list after their creation.
Usage: Suitable for scenarios with frequent reads and infrequent writes, such as lists of event listeners.

// Example of using CopyOnWriteArrayList
import java.util.concurrent.CopyOnWriteArrayList;

public class COWListExample {

    public static void main(String[] args) {
        CopyOnWriteArrayList<String> list = new CopyOnWriteArrayList<>();

        // Adding an element - creates a new copy
        list.add("Element 1");

        // Reading elements - fast
        for (String item : list) {
            System.out.println(item);
        }

        // Snapshot iterator
        // This iterator will see only "Element 1"
        java.util.Iterator<String> iterator = list.iterator();

        // Adding another element - creates another copy
        list.add("Element 2");

        // Printing elements via iterator - only "Element 1" is visible
        while (iterator.hasNext()) {
            System.out.println("From iterator: " + iterator.next());
        }

        // Printing elements from list - both elements are visible
        System.out.println("From list: " + list);
    }
}

Thus, CopyOnWriteArrayList is a good choice when thread safety during reading is critical and write operations are rare. Otherwise, other thread-safe collections like Collections.synchronizedList() or ConcurrentLinkedQueue might be more efficient.

What is the feature of using CopyOnWriteArrayList?