Convert a given tree to its Sum Tree Given a Binary Tree

sumTree.java

// Convert a given tree to its Sum Tree Given a Binary Tree where each node has positive and negative values. Convert this to a tree where each node contains the sum of the left and right sub trees in the original tree. The values of leaf nodes are changed to 0.
// http://www.geeksforgeeks.org/convert-a-given-tree-to-sum-tree/
class Node 
{
    int data;
    Node left, right;

    Node(int item) 
    {
        data = item;
        left = right = null;
    }
}

class BinaryTree 
{
    Node root;

    // Convert a given tree to a tree where every node contains sum of
    // values of nodes in left and right subtrees in the original tree
    int toSumTree(Node node) 
    {
        if (node == null)
           return 0;
        
        int ori = node.data;
        
        node.data = toSumTree(node.left) + toSumTree(node.right);
        
        return (node.data + ori);
        
    }

    // A utility function to print inorder traversal of a Binary Tree
    void printInorder(Node node) 
    {
        if (node == null)
            return;
        printInorder(node.left);
        System.out.print(node.data + " ");
        printInorder(node.right);
    }

    /* Driver function to test above functions */
    public static void main(String args[]) 
    {
        BinaryTree tree = new BinaryTree();

        /* Constructing tree given in the above figure */
        tree.root = new Node(10);
        tree.root.left = new Node(-2);
        tree.root.right = new Node(6);
        tree.root.left.left = new Node(8);
        tree.root.left.right = new Node(-4);
        tree.root.right.left = new Node(7);
        tree.root.right.right = new Node(5);

        tree.toSumTree(tree.root);

        // Print inorder traversal of the converted tree to test result 
        // of toSumTree()
        System.out.println("Inorder Traversal of the resultant tree is:");
        tree.printInorder(tree.root);
    }
}