Java's BlockingQueue interface is a part of the java.util.concurrent package that provides a thread-safe implementation of the queue data structure. It extends the Queue interface and adds the functionality of blocking operations.

BlockingQueue provides four blocking operations:

1. put() - Inserts an element into the queue, if there is no space, it waits until space becomes available.
2. take() - Removes and returns an element from the queue, if the queue is empty, it waits until an element is available.
3. offer() - Inserts an element into the queue, if there is no space, it returns false immediately.
4. poll() - Removes and returns an element from the queue, if the queue is empty, it returns null immediately.

BlockingQueue can be used in a multithreaded environment to coordinate communication between threads. One thread can put an item into the queue, and another thread can take the item out of the queue. If the queue is full or empty, the threads will block until the item is available or there is space in the queue.

There are several implementations of the BlockingQueue interface, including:

• ArrayBlockingQueue: A fixed-size array-based implementation.
• LinkedBlockingQueue: An optionally bounded implementation using a linked list.
• PriorityBlockingQueue: An unbounded implementation that orders elements based on their natural ordering or a Comparator.

To use a BlockingQueue, you create an instance of the implementation of your choice, and then use its methods to put and take items from the queue.