Top view of binary tree using recursion in java

Java program for Top view of binary tree using recursion. Here more information.

/* 
  Java program for
  Top view of binary tree using dfs
*/
// Binary Tree Node
class TreeNode
{
    public int data;
    public TreeNode left;
    public TreeNode right;
    public TreeNode(int data)
    {
        // Set node value
        this.data = data;
        this.left = null;
        this.right = null;
    }
}
public class BinaryTree
{
    public TreeNode root;
    public int level;
    public BinaryTree()
    {
        // Set the initial value of root
        this.root = null;
        this.level = 0;
    }
    // Print left side top nodes including root
    public void printleftSide(TreeNode node, int depth)
    {
        if (node != null)
        {
            if (this.level < depth)
            {
                // Print the resultant node
                System.out.print("  " + node.data);
                this.level = depth;
            }
            // Recursively
            // Visit left subtree
            printleftSide(node.left, depth + 1);
            // Visit right subtree
            printleftSide(node.right, depth - 1);
        }
    }
    // Print right side top nodes
    public void printRightSide(TreeNode node, int depth)
    {
        if (node != null)
        {
            if (this.level < depth)
            {
                // Print the resultant node
                System.out.print("  " + node.data);
                this.level = depth;
            }
            // Recursively
            // First visit right subtree
            printRightSide(node.right, depth + 1);
            // Then
            // Visit left subtree
            printRightSide(node.left, depth - 1);
        }
    }
    // This is handle the request of printing top view
    public void topView()
    {
        this.level = -1;
        printleftSide(this.root, 0);
        this.level = 0;
        printRightSide(this.root, 0);
    }
    public static void main(String[] args)
    {
        // Create new tree
        BinaryTree tree = new BinaryTree();
        /*   Make A Binary Tree
        -----------------------
                 1
               /   \
              2     3
             /     / \
            4     5   6
           /       \    
          7         8    
                     \
                      9
                       \
                        10
        */
        // Construct binary tree
        tree.root = new TreeNode(1);
        tree.root.left = new TreeNode(2);
        tree.root.right = new TreeNode(3);
        tree.root.right.right = new TreeNode(6);
        tree.root.right.left = new TreeNode(5);
        tree.root.left.left = new TreeNode(4);
        tree.root.left.left.left = new TreeNode(7);
        tree.root.right.left.right = new TreeNode(8);
        tree.root.right.left.right.right = new TreeNode(9);
        tree.root.right.left.right.right.right = new TreeNode(10);
        // Display top view
        tree.topView();
    }
}

Output

  1  2  4  7  3  6  10