//package DataStructures;

/**
 * Interface for a priority queue. <p>
 *
 * The <tt>remove</tt> method returns an item of highest priority from
 * the queue.<p>  
 *
 * If distinct items are of the same priority, an implementation is
 * not obliged to return them in any particular order, unless it
 * declares otherwise.<p>
 * 
 * @author Peter Williams
 * @see <a href="http://java.sun.com/products/j2se/1.4/docs/api/java/lang/Comparable.html">Comparable</a> */

public interface PriorityQueue {
    /**
     * Indicates the status of the queue.
     * @return <code>true</code> if the queue is empty.
     */
    public boolean isEmpty();

    /**
     * Returns the current size of the queue
     * @return the current size of the queue
     */
    public int size();

    /**
     * Adds an item to the queue.
     * @param <code>item</code> the item to be added.
     */
    public void add(Comparable item);

    /**
     * Removes an item of highest priority from the queue.
     * @return an item of highest priority.
     * @exception NoSuchElementException if the queue is empty.
     */
    public Comparable remove();
}