construct a linked list from 2d matrix in scala

Scala program for construct a linked list from 2d matrix. Here more information.

// Scala program for
// Construct a linked list from 2D matrix
class LinkNode(var data: Int,
	var next: LinkNode,
		var down: LinkNode)
{
	def this(data: Int)
	{
		this(data, null, null);
	}
}
class DoublyLinkedList(var head: LinkNode)
{
	def this()
	{
		this(null);
	}
	def display(): Unit = {
		if (this.head == null)
		{
			print("Empty linked list");
		}
		else
		{
			var front: LinkNode = this.head;
			var right: LinkNode = null;
			while (front != null)
			{
				right = front;
				while (right != null)
				{
					print("  " + right.data );
					right = right.next;
				}
				print("\n");
				// Visit to down node
				front = front.down;
			}
		}
	}
	def insertData(matrix: Array[Array[Int]], 
        rows: Int, cols: Int): Unit = {
		// Some auxiliary variables
		var levelHead: LinkNode = null;
		var root: LinkNode = null;
		var perv: LinkNode = null;
		var i: Int = 0;
		var j: Int = 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 += 1;
		}
		// 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 += 1;
			}
			levelHead = root;
			// reset col
			j = 0;
			// change row
			i += 1;
		}
	}
}
object Main
{
	def main(args: Array[String]): Unit = {
		var dll: DoublyLinkedList = new DoublyLinkedList();
		// Create 2D metrix
		var matrix: Array[Array[Int]] = Array(
          Array(1, 6, 9, 2, -9), 
          Array(2, 5, -5, 7, 1), 
          Array(3, 4, 1, 8, 2)
        );
		var rows: Int = matrix.length;
		var cols: Int = 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