diff --git a/problems/0102.二叉树的层序遍历.md b/problems/0102.二叉树的层序遍历.md
index e62a3e66..a57a92aa 100644
--- a/problems/0102.二叉树的层序遍历.md
+++ b/problems/0102.二叉树的层序遍历.md
@@ -1528,6 +1528,29 @@ public:
 ```
 
 Java： 
+```Java
+class Solution {
+    public int maxDepth(TreeNode root) {
+        if (root == null)   return 0;
+        Queue<TreeNode> que = new LinkedList<>();
+        que.offer(root);
+        int depth = 0;
+        while (!que.isEmpty())
+        {
+            int len = que.size();
+            while (len > 0)
+            {
+                TreeNode node = que.poll();
+                if (node.left != null)  que.offer(node.left);
+                if (node.right != null) que.offer(node.right);
+                len--;
+            }
+            depth++;
+        }
+        return depth;
+    }
+}
+```
 
 
 Python：