public interface Cs132List 
{
    // Purpose: returns true iff list has no elements
    public boolean isEmpty();

    // Purpose: returns number of elements in the list
    public int size();

    // Purpose: add given data newElement to beginning of list.
    public void addFirst(Object newElement);

    // Purpose: add given data newElement to end of list.
    public void addLast(Object newElement);

    // Purpose: add given data newElement to list at position index (where
    //          0 is the index of the first item in the list, 1 is the
    //          index of the 2nd item in the list, etc.)
    //          What if the index is not inside the given list?
    //          For now, we'll defer that.
    //          BUT note --- those elements "after" this position ARE
    //          shifted "up" a position!
    public void add(int index, Object newElement);

    // Purpose: IF list is not empty, return FIRST element in list.
    //          (we're deferring, for NOW, what to do if list IS empty.)
    public Object getFirst();

    // Purpose: IF the list is not empty, return the LAST element in list.
    //          (we're deferring, for NOW, what to do if the list IS empty.)
    public Object getLast();

    // Purpose: return the element at position index in the list
    //          (where 0 is the index of the first item in the list).
    //          If the index is not within the bounds of this list,
    //          return null.
    public Object get(int index);

    // Purpose: This seeks to remove the element at position index
    //          of the list (where 0 is the index of
    //          the first element in the list). It will do so and return
    //          true if the index is indeed a position in the list and
    //          if the list is not empty --- otherwise, it will return
    //          false and the calling list will remain unchanged.
    //          (elements "above" this in the list are now one
    //          position "lower")
    public Object remove(int index);

    // Purpose: empties the list 
    public void clear();
}