Can you explain the main differences between Queue and Deque data structures?

Queue and Deque are data structures for storing elements with a specific order of removal, but with different capabilities:

• Queue — a data structure that operates on the FIFO (First In, First Out) principle. Elements are added at the end and removed from the beginning. Example: task queue.

• Deque (double-ended queue) — an extension of Queue that allows adding and removing elements from both the front and the end. This provides more flexibility, for example, for implementing a stack or a queue.

In Java, the Queue interface supports operations like offer(), poll(), peek(), while Deque adds methods like addFirst(), addLast(), removeFirst(), removeLast(), etc.

Example of using Deque as a stack:

Deque<Integer> stack = new ArrayDeque<>();
stack.push(1); // adds element on top
stack.push(2);
int top = stack.pop(); // retrieves 2

Thus, Deque is more versatile than Queue.