/** An interface for the ADT list.
 *  Entries in the list have positions that begin with 1.
 */
public interface ListInterface
{
	/** Task: Adds a new entry to the end of the list.
	 *  @param newEntry  the object to be added as a new entry
	 *  @return true if the addition is successful, or false if not */
	public boolean add(Object newEntry);

	/** Task: Adds a new entry at a specified position within
	 *        the list. Entries originally at and above the specified
	 *        position are at the next higher position within the list.
	 *        The listās size is increased by 1.
	 *  @param newPosition  an integer that specifies the desired
	 *                      position of the new entry; newPosition >= 1
	 *                      and newPosition <= getLength()+1
	 *  @param newEntry     the object to be added as a new entry
	 *  @return true if the addition is successful, or false if not */
	public boolean add(int newPosition, Object newEntry);

	/** Task: Removes the entry at a given position from the list.
	 *        Entries originally at positions higher than the given
	 *        position are at the next lower position within the list,
	 *        and the listās size is decreased by 1.
	 *  @param givenPosition  an integer that indicates the position of
	 *                        the entry to be removed; givenPosition >= 1
	 *                        and givenPosition <= getLength()
	 *  @return either the entry at position givenPosition, if the removal
	 *          was successful, or null */
	public Object remove(int givenPosition);

	/** Task: Removes all entries from the list. */
	public void clear();

	/** Task: Replaces the entry at a given position in the list.
	 *  @param givenPosition  an integer that indicates the position of the
	 *                        entry to be replaced; givenPosition >= 1
	 *                        and givenPosition <= getLength()
	 *  @param newEntry  the object that will replace the entry at the
	 *                   position givenPosition
	 *  @return true if the replacement occurs, or false if either the
	 *          list was empty or givenPosition is invalid */
	public boolean replace(int givenPosition, Object newEntry);

	/** Task: Retrieves the entry at a given position in the list.
	 *  @param givenPosition  an integer that indicates the position of
	 *                        the desired entry; givenPosition >= 1
	 *                        and givenPosition <= getLength()
	 *  @return a reference to the indicated list entry, if found,
	 *          otherwise returns null */
	public Object getEntry(int givenPosition);

	/** Task: Determines whether the list contains a given entry.
	 *  @param anEntry  the object that is the desired entry
	 *  @return true if the list contains anEntry, or false if not */
	public boolean contains(Object anEntry);

	/** Task: Gets the length of the list.
	 *  @return the integer number of entries currently in the list */
	public int getLength();

	/** Task: Determines whether the list is empty.
	 *  @return true if the list is empty, or false if not */
	public boolean isEmpty();

	/** Task: Determines whether the list is full.
	 *  @return true if the list is full, or false if not */
	public boolean isFull();

	/** Task: Displays all entries that are in the list, one per
	 *        line, in the order in which they occur in the list. */
	public void display();
} // end ListInterface