Can someone explain why 

temp.setNext(current.getNext()); has been used I am not understanding

public void add(Object data, int index)
        // post: inserts the specified element at the specified position in this list.
        {
                Node temp = new Node(data);
                Node current = head;
                // crawl to the requested index or the last element in the list,
                // whichever comes first
                for(int i = 1; i < index && current.getNext() != null; i++)
                {
                        current = current.getNext();
                }
                // set the new node's next-node reference to this node's next-node reference
                temp.setNext(current.getNext());
                // now set this node's next-node reference to the new node
                current.setNext(temp);
                listCount++;// increment the number of elements variable
        }