public static void main(String args[]){
        BinaryTree bt = new BinaryTree();
        Node head = null;
        head = bt.addNode(100, head);
        head = bt.addNode(90, head);
        head = bt.addNode(10, head);
        head = bt.addNode(15, head);
        head = bt.addNode(25, head);
        head = bt.addNode(5, head);
        head = bt.addNode(7, head);
        head = bt.addNode(-7, head);
        BoundaryTraversal bd = new BoundaryTraversal();
        bd.traversal(head);
    }
http://www.geeksforgeeks.org/boundary-traversal-of-binary-tree/
Test cases
All left children
All right children
Full tree
Complete tree
src/com/interview/tree/BoundaryTraversal.java