/* Cs132PriorityQueue.java 1.0                            */
/* by Sharon Tuttle                                       */
/* last modified: 4-8-03                                  */
/*                                                        */
/* an interface for a priority queue;                     */
/* adapted from pp. 303-304, course text                  */

public interface Cs132PriorityQueue
{
	// can you see that we are in trouble, for a priority queue, if
	// the objects are *not* comparable? how else will we grab the
	// element of lowest value?

    /*------------------------------------------------------------
     getFirst()
     Purpose: return the minimum value in this priority queue
              (non-destructively). Assumes priority queue is NOT
              empty.
    --------------------------------------------------------------*/

	public Comparable getFirst();

	/*-------------------------------------------------------------
     removeFirst()
     Purpose: remove (and return) the minimum value in this priority
              queue ("destructively" --- it DOES change the actual
              priority queue, removing the value). Also assumes
              priority queue is NOT empty.
    ----------------------------------------------------------------*/

    public Comparable removeFirst();

    /*----------------------------------------------------------------
     add()
     Purpose: Assuming that the value to be added is non-null, Comparable
              instance value is added to this priority queue.
    ------------------------------------------------------------------*/

    public void add(Comparable value);

    /*-----------------------------------------------------------------
     isEmpty()
     Purpose: return true if there are no elements in the priority queue,
              false otherwise.
    ---------------------------------------------------------------------*/

    public boolean isEmpty();

    /*-------------------------------------------------------------------
     size()
     Purpose: returns number of elements within the priority queue
    --------------------------------------------------------------------*/
     
    public int size();

    /*-------------------------------------------------------------------
     clear()
     Purpose: removes all elements from priority queue 
    ---------------------------------------------------------------------*/

    public void clear();

}