data-structures/java/Queue/Queue.java

/** Queue ADT */
public interface Queue<E> {
	/** Reinitialize the queue. The user is responsible for reclaiming the storage used by the queue elements. */
	public void clear();

	/** Place an element at the rear of the queue.
	 * @param it The element being enqueued. */
	public void enqueue(E it);

	/** Remove and return element at the front of the queue. 
   * @return The element at the front of the queue. */
  public E dequeue();

  /** @return The front element. */
  public E frontValue();

  /** @return The number of elements in the queue. */
  public int length();
}