A queue is a First-In First-Out (FIFO) data structure, commonly used in situations where you want to process items in the order they are created or queued. It is considered a limited access data structure since you are restricted to removing the oldest element first.
By convention, the queue insert operation is called enqueue and the
remove operation is called dequeue. Since we are mimicking the Java API,
we will stick to the add, offer, poll, and remove.
One common model of usage for a queue is to have one thread adding work to the queue, and another processing work from the queue. This is a common way to architect server programs.
The following image shows a conceptual image of a queue. The front of the queue is where items are removed, and the rear of the queue is where items are added.
Circular Array Queues
During this recitation we will be creating a circular array queue with a maximum capacity. This will give us an idea of how queues are implemented outside of academia. The capacity is a very realistic constraint.
The following image is a visual aid as to how circular array queues work:
If you would like to learn more about circular arrays, go here.