What is a BlockingQueue in Java?

A BlockingQueue is a thread-safe queue that blocks on certain operations: put() blocks if the queue is full (until space becomes available), and take() blocks if the queue is empty (until an element is available). This makes it ideal for the Producer-Consumer pattern without manually managing wait/notify. Implementations: ArrayBlockingQueue (bounded, array-backed), LinkedBlockingQueue (optionally bounded, linked), PriorityBlockingQueue (unbounded, sorted), SynchronousQueue (no capacity, direct handoff between threads). BlockingQueues are thread-safe and avoid the boilerplate of synchronized blocks for inter-thread data exchange.