/**
 * Interface for Queue
 * Names follow textbook rather than Java standard
 * @author gtowell
 * Created: Sep 2019
 * Modified: Oct 20, 2020
 * Modified: mar 26, 2021
 * Modified: Aug 9, 2021
 */
public interface QueueInterface<E> {
    /**
     * The number of items in the queue
     * @return the number of items in the queue
     * **/
    int size();

    /**
     * returns true iff the queue contains no items
     * @return true iff the queue contains no items
     */    
    boolean isEmpty();
    
    /**
     * The next item in the queue.   This is distinct from poll in that this returns 
     * the next items in the queue but DOES NOT remove it from the queue. 
     * @return the next item in the queue or NULL if the queue is empty
     */
    E getFront();
    
    /**
     * Add an item to the queue.
     * @param e the item to be added
     * @return true if the item could be added to the queue.  False otherwise
     */
    boolean enqueue(E e);

    /**
     * Remove and return the item from the front of the queue.  Distinst from peek in that
     * this removes the first item in addition to returning it.
     * @return the first item, or null iff the queue is empty.
     */
    E dequeue(); // remove from, and return the first item in q
    
    /**
     * Remove all elements from the queue
     * As a result, after executing this method, isEmpty() will return true
     */
    void clear();
}