Serialize and Deserialize 3-ray tree

A 3-ary tree is where every node has 3 children. Given a string of serialized tree, How to deserialze and serialize it? 

Solution:

import java.util.LinkedList;

public class SerializeDeserializeTree {
    public static void main(String[] args) {
  
        String tree = "1,1,2,3,1,2,3,1,#,#,#,#,3";
        TreeNode root = deserialize(tree);
  
        System.out.print("serializeTree: "+serializeTree(root));
  
    }
 
    public static class TreeNode {
        int val;
        TreeNode[] child;
        TreeNode(int x) {
            this.val = x;
            this.child = new TreeNode[3];
        }
    }
 
    public static int getDepth(TreeNode root) {
        if(root == null) {
            return 0;
        }
        return Math.max(Math.max(getDepth(root.child[0]), getDepth(root.child[1])), getDepth(root.child[2])) + 1;
    }
    

    //serialize
    public static String serializeTree(TreeNode root) {
        if(root == null) {
            return "#";
        }
  
        StringBuilder res = new StringBuilder();
        LinkedList queue = new LinkedList();
        int depth = getDepth(root);
        queue.add(root);
        res.append(root.val).append(",");
        int last = 1;
        int cur = 0; 
        int level = 1;
        while(!queue.isEmpty()) {
            TreeNode node = queue.poll();
            last--;
            if(node.child[0] != null) {
                res.append(node.child[0].val).append(",");
                queue.add(node.child[0]);
                cur++;
            }else if(level < depth){
                res.append("#").append(",");
            }
   
            if(node.child[1] != null) {
                res.append(node.child[1].val).append(",");
                queue.add(node.child[1]);
                cur++;
            }else if(level < depth){
                res.append("#").append(",");
            }
   
            if(node.child[2] != null) {
                res.append(node.child[2].val).append(",");
                queue.add(node.child[2]);
                cur++;
            }else if(level < depth){
                res.append("#").append(",");
            }
   
            if(last == 0 && !queue.isEmpty()) {
                last = cur;
                cur = 0;
                level++;
            } 
        }
        res = res.deleteCharAt(res.length() - 1);
        return res.toString();
   }
 
   //deserialize
   public static TreeNode deserialize(String tree) {
       if (tree == null || tree.length() == 0)
           return null;

       String[] nodes = tree.split(",");
       if (nodes[0] == "#")
           return null;

       TreeNode root = new TreeNode(Integer.parseInt(nodes[0]));
       LinkedList queue = new LinkedList();
       queue.add(root);
       for (int i = 1; i < nodes.length; i = i + 3) {
           TreeNode r = queue.poll();
           if (!nodes[i].equals("#")) {
               TreeNode n = new TreeNode(Integer.parseInt(nodes[i]));
               queue.add(n);
               r.child[0] = n;
           }
           if (!nodes[i + 1].equals("#")) {
               TreeNode n = new TreeNode(Integer.parseInt(nodes[i + 1]));
               queue.add(n);
               r.child[1] = n;
           }
           if(!nodes[i + 2].equals("#")) {
               TreeNode n = new TreeNode(Integer.parseInt(nodes[i + 2]));
               queue.add(n);
               r.child[2] = n;
           }
       }
  
       return root;
   }
}