Inorder traversal of binary tree with recursion in scala

Scala program for Inorder traversal of binary tree with recursion. Here problem description and explanation.

/* 
  Scala Program for
  inorder tree traversal of a Binary Tree
  using recursion
*/
// Binary Tree Node
class TreeNode(var data: Int,
	var left: TreeNode,
		var right: TreeNode)
{
	def this(data: Int)
	{
		// Set node value
		this(data, null, null);
	}
}
class BinaryTree(var root: TreeNode)
{
	def this()
	{
		this(null);
	}
	// Display Inorder view of binary tree
	def inorder(node: TreeNode): Unit = {
		if (node != null)
		{
			// Visit left subtree
			inorder(node.left);
			// Print node value
			print("  " + node.data);
			// Visit right subtree
			inorder(node.right);
		}
	}
}
object Main
{
	def main(args: Array[String]): Unit = {
		// Create new tree
		var tree: BinaryTree = new BinaryTree();
		/*
		    Make A Binary Tree
		    ----------------
		        15
		       /  \
		      24   54
		     /    /  \
		    35   62   13
		*/
		// Add tree TreeNode
		tree.root = new TreeNode(15);
		tree.root.left = new TreeNode(24);
		tree.root.right = new TreeNode(54);
		tree.root.right.right = new TreeNode(13);
		tree.root.right.left = new TreeNode(62);
		tree.root.left.left = new TreeNode(35);
		// Display Tree Node
		tree.inorder(tree.root);
	}
}

Output

  35  24  15  62  54  13