printAllPaths

/**
     * print all paths from root to leaf node
     * using a helper function
     * path is an array to store current nodes on the path
     */
    public void printAllPaths(){
        TreeNode[] path = new TreeNode[100];
        printAllPathHelper(root, path, 0);
    }

    private void printAllPathHelper(TreeNode n,TreeNode[] path, int length){
        if(n == null){
            return;
        }
        path[length] = n;
        length++;
        //reached to the leaf node
        if(n.leftChild==null&&n.rightChild==null){
            printPath(path,length);
        }else{
            printAllPathHelper(n.leftChild, path, length);
            printAllPathHelper(n.rightChild, path, length);
        }
    }

    private void printPath(TreeNode []path,int length){
        int i = 0;
        while(i<length){
            System.out.print(path[i].data+" ");
            i++;
        }
        System.out.println();
    }