public class LinkedList
{
    private LinkedListNode head;
    
    public LinkedList()
    {
        head = null;
    }
    
    /**
     * Insert an object into the front of a linked list
     * @param obj The object to insert
     */
    public void insert(Object obj)
    {
        head = new LinkedListNode(obj, head);
    }
    
    
    /**
     * Insert an object into the end of a linked list
     * @param obj The object to insert
     */
    public void insertAtEnd(Object obj)
    {
        // TODO:  Fill me in!
    }

    
    /**
     * Delete the first element from the linked list
     * return the object that was deleted
     * @return The object that was deleted from the list
     */
    public Object deleteFirst()
    {
        // TODO:  Fill me in!
        return null;
    }

    /** 
     * Delete the last element from the linked list.
     * Return the object that was deleted.
     * @return
     */
    public Object deleteLast()
    {
        // TODO:  Fill me in!
        return null;
    }
    
    // Method removeAt(int index)
    //  Removes the Object o at the specified index.  If index == 0, the first element 
    //  in the list is removed, if index == 1, the second element in the list is
    //  removed, and so on.
    //  No error checking is done for the range of index -- an index outside the range
    //  will can a null pointer exception
    //  Return the object that was removed.
    public Object removeAt(int index)
    {
        return null;
        // Fill Me In!
    }
   
    
    // Method remove(Object o)
    //  Removes the first occurrence of the Object o from the list.  If
    //    the object appears more than once, only the first occurrence is
    //    removed.  If the object does not occur in the list, the method
    //    does nothing.  This one is tricky!
    public void remove(Object o)
    {
        
    }
    
    
    // Method remove(Object o)
    //  Removes the first occurrence of the Object o from the list.  If
    //    the object appears more than once, only the first occurrence is
    //    removed.  If the object does not occur in the list, the method
    //    does nothing.  This one is tricky!
    public void removeAll(Object o)
    {
        
    }
    
    
    public String toString()
    {
        String returnString;
        if (head == null)
        {
            returnString =  "[]";
        }
        else
        {
            returnString = "["+head.data.toString();
            LinkedListNode tmp = head.next;
            while (tmp != null)
            {
                returnString = returnString + ", " + tmp.data.toString();
                tmp = tmp.next;
            }
            returnString = returnString + "]";
        }
        return returnString;
    }
    
}