public interface ListInterface <T>{
  public boolean isEmpty();
  // Determines whether a list is empty.
  // Precondition: None.
  // Postcondition: Returns true if the list is empty,
  // otherwise returns false.
  // Throws: None.

  public int size();
  // Determines the length of a list.
  // Precondition: None.
  // Postcondition: Returns the number of items that are
  // currently in the list.
  // Throws: None.

  public void removeAll();
  // Deletes all the items from the list.
  // Precondition: None.
  // Postcondition: The list is empty.
  // Throws: None.
  
  public void add(int index, T item) 
           throws ListIndexOutOfBoundsException,
                  ListException;
  // Adds an item to the list at position index.
  // Precondition: index indicates the position at which  
  // the item should be inserted in the list.
  // Postcondition: If insertion is successful, item is 
  // at position index in the list, and other items are
  // renumbered accordingly.
  // Throws: ListIndexOutOfBoundsException if index < 1 or 
  // index > size()+1.
  // Throws: ListException if item cannot be placed on 
  // the list.

  public T get(int index) throws
        ListIndexOutOfBoundsException;
  // Retrieves a list item by position.
  // Precondition: index is the number of the item to be
  // retrieved.
  // Postcondition: If 1 <= index <= size(), the item at
  // position index in the list is returned.
  // Throws: ListIndexOutOfBoundsException if index < 1 or 
  // index > size().

  public void remove(int index) 
              throws ListIndexOutOfBoundsException;
  // Deletes an item from the list at a given position.
  // Precondition: index indicates where the deletion 
  // should occur. 
  // Postcondition: If 1 <= index <= size(), the item at 
  // position index in the list is deleted, and other items
  // are renumbered accordingly.
  // Throws: ListIndexOutOfBoundsException if index < 1 or 
  // index > size().
}