/**
   Thrown when an attempt is made to add an item to a priority queue
   the key of which has a type different from the keys expected.
 
   @author      Franck van Breugel
   @version     1.1   June 30, 2000
*/
public class InvalidKeyException extends RuntimeException 
{
    /** 
       Constructs an InvalidKeyException without error message.
     */
    public InvalidKeyException() 
    {
        super();
    }

    /** 
       Constructs an InvalidKeyException with the specified error message.
      
       @param errorMessage Error message.
    */
    public InvalidKeyException(String errorMessage) 
    {
        super(errorMessage);
    }
}