// Introduced in Chapter 4
/** A first-in, first-out queue of Objects. */
public interface Queue<E> {

  /** Add target to the back of this Queue. */
  public void add(E target);

  /** Return true if this Queue is empty. */
  public boolean isEmpty();

  /**
   * Remove and return the front item from this Queue.
   * @throws EmptyStructureException if the Queue is empty.
   */
  public E remove();

}