public static void main(String args[]){
        BinaryTreeToCircularLinkList btc = new BinaryTreeToCircularLinkList();
        BinaryTree bt = new BinaryTree();
        Node root = null;
        root = bt.addNode(10, root);
        root = bt.addNode(3, root);
        root = bt.addNode(-1, root);
        root = bt.addNode(8, root);
        root = bt.addNode(-6, root);
        root = bt.addNode(13, root);
        root = btc.convert(root);
        btc.print(root);
    }
http://cslibrary.stanford.edu/109/TreeListRecursion.html
Test cases
Null tree
src/com/interview/tree/BinaryTreeToCircularLinkList.java