Queue, Deque & Stack

ArrayDeque is the fastest Deque/Stack/Queue implementation in Java, backed by a circular array with O(1) operations at both ends, beating LinkedList in speed and Stack in design.

LinkedBlockingQueue is a thread-safe FIFO queue with two separate locks for put and take, where put() blocks when full and take() blocks when empty, making it the standard choice for producer-consumer patterns.

CopyOnWriteArrayList is a thread-safe List where every write copies the entire internal array, making reads lock-free and iterators snapshot-based, ideal for read-heavy scenarios with rare writes.

PriorityQueue is a min-heap where only the head is guaranteed to be the smallest element; use it for repeated min/max extraction. Use a sorted list or TreeSet when you need all elements in order.

Queue offers two method variants for each operation: throwing (add/remove/element) for when failure is a bug, and special-value (offer/poll/peek) for when empty or full is a normal runtime condition.

ArrayDeque provides push/pop/peek for LIFO stack behavior backed by a circular array, replacing the legacy Stack class which extends synchronized Vector and exposes non-stack methods.

BlockingDeque is a double-ended blocking queue where both ends support blocking put and take, enabling work-stealing patterns where workers take from their own head and steal from others' tails.

TransferQueue's transfer(e) blocks the producer until a consumer actually takes the element, providing guaranteed hand-off unlike put(e) which is fire-and-forget.