/*
 * Created on Apr 26, 2005
 */
package stockportfolio;

/** An enhanced queue which permits which permits additional operations,
 * such as pushing an element on the front.
 */
public interface IDQueue extends IQueue {
    
    /** Add (push) an element to the front of the queue; thus, the next dequeue
     * operation would return this value, assuming there were no other
     * intervening addToFront operations.
     * @param newValue a non-null object
     * @return true iff the object was successfully added to the queue.
     * @throws IllegalArgumentException if the new value is null.
     */
    boolean addToFront(Object newValue);
    
    /** Get an object from the queue.  The object is not dequeued 
     * and the stack is unchanged.
     * @param index an index number, with 0 being the oldest object
     * (i.e., the one at the front of the queue), 1 being
     * next oldest, etc.
     * @return the object corresponding to blocknum
     * @throws IllegalArgumentException if index is not a valid index.
     */
    Object getObject(int index);

}