list.java

为什么这个网站要弄这么麻烦啊？？真是搞不明白

public interface List {
  public int size();
  public boolean isEmpty();
  public boolean isFirst(Position p) throws InvalidPositionException;
  public boolean isLast(Position p) throws InvalidPositionException;
  public Position first() throws EmptyContainerException;
  public Position last() throws EmptyContainerException;
  public Position before (Position p)  
    throws InvalidPositionException, BoundaryViolationException;
  public Position after (Position p) 
    throws InvalidPositionException, BoundaryViolationException;
  public Position insertBefore (Position p, Object element) 
    throws InvalidPositionException;
  public Position insertAfter (Position p, Object element) 
    throws InvalidPositionException;
  public Position insertFirst(Object element);
  public Position insertLast(Object element);
  public Object remove(Position p) throws InvalidPositionException;
  public Object replaceElement (Position p, Object element)  
    throws InvalidPositionException;
  public void swapElements (Position a, Position b)
    throws InvalidPositionException;
}