In Java, the Queue interface is a part of the Java Collections Framework that defines a collection for holding elements prior to processing. A queue is a data structure that follows the First-In-First-Out (FIFO) order, meaning that the first element added to the queue will be the first one to be removed.

The Queue interface is extended by the Deque interface which allows adding and removing elements from both ends of the queue. The Queue interface provides several methods for adding, removing, and examining elements. Here are some of the key methods defined in the Queue interface:

• boolean add(E element): Adds the specified element to the end of the queue.

• boolean offer(E element): Adds the specified element to the end of the queue and returns true if successful.

• E remove(): Removes and returns the element at the front of the queue.

• E poll(): Removes and returns the element at the front of the queue or returns null if the queue is empty.

• E element(): Returns the element at the front of the queue without removing it.

• E peek(): Returns the element at the front of the queue without removing it, or returns null if the queue is empty.

The Queue interface is implemented by several classes in the Java Collections Framework, such as LinkedList and PriorityQueue. These classes provide different implementations of the queue data structure with varying performance characteristics and ordering guarantees.

The Queue interface is useful for implementing algorithms that require processing elements in a specific order, such as breadth-first search or message processing systems.