code: public void addLast(final T node) {
          if ( this.firstNode == null ) {
              this.firstNode = node;
              this.lastNode = node;
          } else {
              T currentLast = this.lastNode;
              currentLast.setNext( node );
              node.setPrevious( currentLast );
              this.lastNode = node;            
          }
          
          this.size++;
      }
docs: Add a <code>LinkedListNode</code> to the end of the list. If the <code>LinkedList</code> is empty then the first and
  last nodes are set to the added node.
  
  @param node
  The <code>LinkedListNode</code> to be added