Insertion in binary search tree without recursion in scala

Scala program for Insertion in binary search tree without recursion. Here problem description and explanation.

// Scala program for
// iterative insert in binary search tree
class TreeNode(var data: Int,
	var left: TreeNode,
		var right: TreeNode)
{
	def this(data: Int)
	{
		this(data, null, null)
	}
}
class BinarySearchTree(var root: TreeNode)
{
	def this()
	{
		this(null)
	}
	//insert a element
	def addNode(data: Int): Unit = {
		// Create a new node
		var node: TreeNode = new TreeNode(data);
		if (this.root == null)
		{
			// When adds a first node in bst
			this.root = node;
		}
		else
		{
			var find: TreeNode = this.root;
			// Add new node to proper position
			while (find != null)
			{
				if (find.data >= data)
				{
					if (find.left == null)
					{
						// When left child empty
						// So add new node here
						find.left = node;
						return;
					}
					else
					{
						// Otherwise
						// Visit left sub-tree
						find = find.left;
					}
				}
				else
				{
					if (find.right == null)
					{
						// When right child empty
						// So add new node here
						find.right = node;
						return;
					}
					else
					{
						// Visit right sub-tree
						find = find.right;
					}
				}
			}
		}
	}
	// Display preorder
	def preorder(node: TreeNode): Unit = {
		if (node != null)
		{
			// Display node value
			print("  " + node.data);
			// Visit to left subtree
			preorder(node.left);
			// Visit to right subtree
			preorder(node.right);
		}
	}
	def inorder(node: TreeNode): Unit = {
		if (node != null)
		{
			// Visit to left subtree
			inorder(node.left);
			// Display node value
			print("  " + node.data);
			// Visit to right subtree
			inorder(node.right);
		}
	}
	def postorder(node: TreeNode): Unit = {
		if (node != null)
		{
			// Visit to left subtree
			postorder(node.left);
			// Visit to right subtree
			postorder(node.right);
			// Display node value
			print("  " + node.data);
		}
	}
}
object Main
{
	def main(args: Array[String]): Unit = {
		var tree: BinarySearchTree = new BinarySearchTree();
		/*
		         10
		        / \
		       /   \
		      4     15
		     / \   /
		    3   5 12
		    -------------
		    Build binary search tree

		*/
		tree.addNode(10);
		tree.addNode(4);
		tree.addNode(3);
		tree.addNode(5);
		tree.addNode(15);
		tree.addNode(12);
		// Display tree nodes
		println("Preorder ");
		tree.preorder(tree.root);
		println("\nInorder ");
		tree.inorder(tree.root);
		println("\nPostorder ");
		tree.postorder(tree.root);
	}
}

Output

Preorder
  10  4  3  5  15  12
Inorder
  3  4  5  10  12  15
Postorder
  3  5  4  12  15  10