/**
   The PriorityQueue interface specifies a collection of prioritized elements 
   that supports arbitrary additions and removals in order of priority.
   A prioritized element, or item, is an element together with a key.
  
   @author      Franck van Breugel
   @version     1.1    October 25, 1999
*/
public interface PriorityQueue 
{
    /** 
       Returns the size of this priority queue. 

       @return The size of this priority queue.
    */
    int size();

    /** 
       Tests if this priority queue is empty. 

       @return true if this priority queue is empty, false otherwise.
    */
    boolean isEmpty();

    /**
       Adds the specified element with the specified key to the priority queue.

       @param key Key of element to be added.
       @param element Element to be added.
    */
    void insertItem(Object key, Object element);

    /**
       Returns an element with the smallest key in this priority queue.

       @return Element with the smallest key.
       @exception EmptyContainerException if this priority queue is empty.
    */
    Object minElement() throws EmptyContainerException;

    /**
       Returns the smallest key in this priority queue.

       @return The smallest key.
       @exception EmptyContainerException if this priority queue is empty.
    */
    Object minKey() throws EmptyContainerException;

    /**
       Removes an item with the smallest key from this priority queue
       and returns the element of the item.

       @return Element of an item with the smallest key.
       @exception EmptyContainerException if this priority queue is empty.
    */
    Object removeMinElement() throws EmptyContainerException;
}