public int findPosNode(T x) {//return position of node
        int pos=0;
        Node<T> ele = _head;
        while (ele != null) {
            if (ele.getData().equals(x))
                return pos;
            else{
            ele = ele.getNext();
            pos+=1;
            }
        }
        return -1;//node is not int the list.
    }