diff --git a/problems/0101.对称二叉树.md b/problems/0101.对称二叉树.md
index 561d0470..b9e203e8 100644
--- a/problems/0101.对称二叉树.md
+++ b/problems/0101.对称二叉树.md
@@ -253,9 +253,13 @@ public:
 
 ## 其他语言版本
 
-
 Java：
 
+```java
+```
+
+
+
 
 Python：
 
@@ -284,4 +288,4 @@ const check = (leftPtr, rightPtr) => {
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)
 * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
-<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
+<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
\ No newline at end of file
diff --git a/problems/0110.平衡二叉树.md b/problems/0110.平衡二叉树.md
index 5d55910c..ee215a68 100644
--- a/problems/0110.平衡二叉树.md
+++ b/problems/0110.平衡二叉树.md
@@ -353,9 +353,13 @@ public:
 
 ## 其他语言版本
 
-
 Java：
 
+```java
+```
+
+
+
 
 Python：
 
@@ -369,4 +373,4 @@ Go：
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)
 * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
-<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
+<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
\ No newline at end of file
diff --git a/problems/0404.左叶子之和.md b/problems/0404.左叶子之和.md
index 8ff2b320..da4ed666 100644
--- a/problems/0404.左叶子之和.md
+++ b/problems/0404.左叶子之和.md
@@ -159,9 +159,51 @@ public:
 
 ## 其他语言版本
 
-
 Java：
 
+**递归**
+
+```java
+class Solution {
+    public int sumOfLeftLeaves(TreeNode root) {
+        if (root == null) return 0;
+        int leftValue = sumOfLeftLeaves(root.left);    // 左
+        int rightValue = sumOfLeftLeaves(root.right);  // 右
+                                                       
+        int midValue = 0;
+        if (root.left != null && root.left.left == null && root.left.right == null) { // 中
+            midValue = root.left.val;
+        }
+        int sum = midValue + leftValue + rightValue;
+        return sum;
+    }
+}
+```
+
+**迭代**
+
+```java
+class Solution {
+    public int sumOfLeftLeaves(TreeNode root) {
+        if (root == null) return 0;
+        Stack<TreeNode> stack = new Stack<> ();
+        stack.add(root);
+        int result = 0;
+        while (!stack.isEmpty()) {
+            TreeNode node = stack.pop();
+            if (node.left != null && node.left.left == null && node.left.right == null) {
+                result += node.left.val;
+            }
+            if (node.right != null) stack.add(node.right);
+            if (node.left != null) stack.add(node.left);
+        }
+        return result;
+    }
+}
+```
+
+
+
 
 Python：
 
@@ -176,3 +218,4 @@ Go：
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)
 * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
 <div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
+