Package com.zybooks.dsaj.stackqueue

Interface Queue<E>

Type Parameters:
E - the element type
All Known Subinterfaces:
CircularQueue<E>
All Known Implementing Classes:
ArrayQueue, LinkedCircularQueue, LinkedQueue
public interface Queue<E>
Interface for a queue: a collection of elements that are added and removed according to the first-in first-out principle. Although similar in purpose, this interface differs from java.util.Queue.

  • Method Summary

    Modifier and Type
    Method
    Description
    E
    dequeue()
    Removes and returns the first element of the queue.
    void
    enqueue(E e)
    Adds an element at the rear of the queue.
    E
    first()
    Returns, but does not remove, the first element of the queue.
    boolean
    isEmpty()
    Tests whether the queue is empty.
    int
    size()
    Returns the number of elements in the queue.

  • Method Details

    • size

      int size()
      Returns the number of elements in the queue.
      Returns:
      number of elements in the queue

    • isEmpty

      boolean isEmpty()
      Tests whether the queue is empty.
      Returns:
      true if the queue is empty, false otherwise

    • enqueue

      void enqueue(E e)
      Adds an element at the rear of the queue.
      Parameters:
      e - the element to be added

    • first

      E first()
      Returns, but does not remove, the first element of the queue.
      Returns:
      the first element of the queue (or null if empty)

    • dequeue

      E dequeue()
      Removes and returns the first element of the queue.
      Returns:
      element removed (or null if empty)