/**
 * Interface to a sequential list of objects.
 * Demonstration program for CSE 143.  
 * @author Hal Perkins
 * @version 0.1, 4/17/06
 */
public interface List<E> {  
  
  // query functions
  
  /**
   * Return the size of this list
   * @return number of items currently in the list
   */
  public int size();
  
  /**
   * Report whether this list is empty or not
   * @return true if the list is empty, otherwise false
   */
  public boolean isEmpty();
  
  /**
   * Return the location of an item in this list
   * @param s the item to be located
   * @return the index of s in the list if it is present, otherwise -1
   */
  public int indexOf(E s);
  
  /**
   * Report whether this list contains a particular item
   * @param s item to search for
   * @return true if s is contained in the list, false otherwise
   */
  public boolean contains(E s);
  
  /**
   * Return the list item at a given position in this list
   * @param pos position of desired item (must be 0 <= pos < size)
   * @return the list item at that position
   */
  public E get(int pos);  
  
  // list modifications
  
  /**
   * Change the item at a given position to a new value
   * @param pos position in the list to be changed (must be 0 <= pos < size)
   * @param s   new value to put at that position
   */
  public void set(int pos, E s);
  
  /**
   * Add a new item to the end of this list.
   * @param s the item to add to the list
   */
  public void add(E s);
  
  /**
   * Add a new item to this list at a specified position
   * @param pos location where item should be added 
   *            (pre: 0 <= pos < size)
   * @param s   item to be added
   */
  public void add(int pos, E s);

  /**
   * Remove the item at the specified position from this list
   * @param pos position of the item to be removed (must be 0 <= pos < size)
   */
  public void remove(int pos);
  
  // toString
  
  /**
   * Return a string representation of this list
   * @return A list of the items in this list separated by commas
   *          and surrounded by brackets
   */
  public String toString(); 
  
}