Binary Tree Level Order Traversal

public ArrayList<ArrayList<Integer>> levelOrder(TreeNode root) {  
        ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();  
        if(root == null) 
            return res;  

        LinkedList<TreeNode> queue = new LinkedList<TreeNode>();  
        queue.add(root);  
        int curLevCnt = 1;  
        int nextLevCnt = 0;  
        ArrayList<Integer> levelres = new ArrayList<Integer>();  

        while(!queue.isEmpty()){  
            TreeNode cur = queue.poll();  
            curLevCnt--;  
            levelres.add(cur.val);  

            if(cur.left != null){  
                queue.add(cur.left);  
                nextLevCnt++;  
            }  
            if(cur.right != null){  
                queue.add(cur.right);  
                nextLevCnt++;  
            }  

            if(curLevCnt == 0){  
                curLevCnt = nextLevCnt;  
                nextLevCnt = 0;  
                res.add(levelres);  
                levelres = new ArrayList<Integer>();  
            }  
        }  
        return res;  
}