public interface Sequence {

   // Generic Container methods:
   public int size();
   public boolean isEmpty();

   // Positional Sequence methods
   public Position insertBefore(Position p, Object e) throws InvalidPositionException;
   public Position insertAfter(Position p, Object e) throws InvalidPositionException;
   public Object remove(Position p) throws InvalidPositionException;
   public Position before(Position p) throws InvalidPositionException;
   public Position after(Position p) throws InvalidPositionException;
   public Position firstPosition() throws EmptyContainerException;
   public Position lastPosition() throws EmptyContainerException;

   // Ranked Sequence methods
   public Object atRank(int rank) throws BoundaryViolationException;
   public void insertAtRank(int rank, Object e) throws BoundaryViolationException;
   public Object remove(int rank) throws BoundaryViolationException;

   // Deque methods
   public Position insertFirst(Object e);
   public Position insertLast(Object e);
   public Object removeFirst() throws EmptyContainerException;
   public Object removeLast() throws EmptyContainerException;
   public Object firstElement() throws EmptyContainerException;
   public Object lastElement() throws EmptyContainerException;

   // Conversion methods for ranks and positions
   public Position positionAtRank(int rank) throws BoundaryViolationException;
   public int rankOf(Position position) throws InvalidPositionException;

}