public interface LinkedListInterface<J> {
    /**
     * Return the number of items in the linked list
     * 
     * @return the number of items in the linked list
     */
    int size();

    /**
     * True iff the linked list has 0 items
     * 
     * @return
     */
    boolean isEmpty();

    /**
     * The "first" item in the linked list. That is the object stored in the first
     * node. The first node is the item in the linked list which is pointed to by no
     * other item in the linked list
     * 
     * @return the object stored in the first node
     */
    J first();

    /**
     * The object stored in the last node of the linked list. Last is the node that
     * points to no other node.
     * 
     * @return the object in the last node
     */
    J last();

    /**
     * Add this item to the linked list after the current last item. So after
     * executing this, a call to last() will return c
     * 
     * @param c the item to be added
     */
    void addLast(J c);

    /**
     * Add the item before the current first item. So after executing this, a call
     * to first() will return c
     * 
     * @param c the object to be added.
     */
    void addFirst(J c);

    /**
     * Remove the first node from this linked list
     * 
     * @return the object stored in the first node
     */
    J removeFirst();

    /**
     * Remove the last node from the linked list
     * 
     * @return the object store in the last node
     */
    J removeLast();

    /**
     * Remove a node containing the provided object. If not found, return false If
     * found, remove from the linked list the node containing r and return true.
     * 
     * @param r the object to be removed.
     * @return true iff the object is in the linked list.
     */
    boolean remove(J r);
}