ArrayDeque

ArrayDeque is a resizable, circular-array implementation of the Deque interface. Use it when you need a queue or a stack today, because it's faster than LinkedList for queue operations and faster than Stack for stack operations. This lesson covers how the circular buffer works internally, why it beats the older alternatives, the rules around nulls and capacity, and a few realistic e-commerce use cases (a job queue for processing orders, a sliding window of recent events, and a modern replacement for the legacy Stack-based undo).