public static void main(String args[]){
        BinaryTreeToDoubleLinkList btd = new BinaryTreeToDoubleLinkList();  
        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);
        btd.toDoubleLL(head);
        btd.print(head);
    }
http://www.geeksforgeeks.org/convert-given-binary-tree-doubly-linked-list-set-3/
src/com/interview/tree/BinaryTreeToDoubleLinkList.java