construct a linked list from 2d matrix in java

Java program for construct a linked list from 2d matrix. Here problem description and other solutions.

// Java program for
// Construct a linked list from 2D matrix
class LinkNode
{
    public int data;
    public LinkNode next;
    public LinkNode down;
    public LinkNode(int data)
    {
        this.data = data;
        this.next = null;
        this.down = null;
    }
}
public class DoublyLinkedList
{
    public LinkNode head;
    public DoublyLinkedList()
    {
        // Set inital value
        this.head = null;
    }
    public void display()
    {
        if (this.head == null)
        {
            System.out.print("Empty linked list");
        }
        else
        {
            LinkNode front = this.head;
            LinkNode right = null;
            while (front != null)
            {
                right = front;
                while (right != null)
                {
                    System.out.print(right.data + "  ");
                    right = right.next;
                }
                System.out.print("\n");
                // Visit to down node
                front = front.down;
            }
        }
    }
    public void insertData(int[][] matrix, int rows, int cols)
    {
        // Some auxiliary variables
        LinkNode levelHead = null, root = null, perv = null;
        int i = 0;
        int j = 0;
        // Add first row elements into result list 
        while (i < cols)
        {
            if (this.head == null)
            {
                // Add first node
                this.head = new LinkNode(matrix[0][i]);
                levelHead = this.head;
            }
            else
            {
                // next head
                levelHead.next = new LinkNode(matrix[0][i]);
                levelHead = levelHead.next;
            }
            i++;
        }
        // Get first element    
        levelHead = this.head;
        i = 1;
        // Add all the bottom element of each column
        while (i < rows)
        {
            root = null;
            perv = root;
            while (j < cols)
            {
                levelHead.down = new LinkNode(matrix[i][j]);
                if (root == null)
                {
                    root = levelHead.down;
                    perv = root;
                }
                else
                {
                    perv.next = levelHead.down;
                    perv = levelHead.down;
                }
                levelHead = levelHead.next;
                j++;
            }
            levelHead = root;
            // reset col
            j = 0;
            // change row
            i++;
        }
    }
    public static void main(String[] args)
    {
        DoublyLinkedList dll = new DoublyLinkedList();
        // Create 2D metrix
        int[][] matrix = {
            {
                1 , 6 , 9 , 2 , -9
            },
            {
                2 , 5 , -5 , 7 , 1
            },
            {
                3 , 4 , 1 , 8 , 2
            }
        };
        int rows = matrix.length;
        int cols = matrix[0].length;
        dll.insertData(matrix, rows, cols);
        dll.display();
    }
}

Output

1  6  9  2  -9
2  5  -5  7  1
3  4  1  8  2