// file:    PriorityQueue.java
// author:  Robert Keller
// purpose: Define a PriorityQueue interface.

/**
 * A Priority is a repository for Objects that can be compared using
 * a Comparator.
 * Objects are inserted using enqueue and removed using dequeueMin,
 * which always returns the minimum based on the Comparator.
 */

interface PriorityQueue
{
/**
 * Insert an Comparable in the PriorityQueue.
 *
 * @param item the Comparable to be inserted
 */

void enqueue(Object item);


/**
 * Remove the minimum Comparable from the PriorityQueue.
 *
 * @return the Comparable removed
 * @exception EmptyQueueException if the PriorityQueue is empty
 */

Object dequeueMin() throws EmptyQueueException;


/**
 * Indicate whether or not the PriorityQueue is empty
 *
 * @return boolean indicating whether or not the Queue is empty
 */

boolean isEmpty();
}