diff --git a/codes/java/chapter_tree/avl_tree.java b/codes/java/chapter_tree/avl_tree.java
new file mode 100644
index 0000000..5666b5d
--- /dev/null
+++ b/codes/java/chapter_tree/avl_tree.java
@@ -0,0 +1,218 @@
+/*
+ * File: avl_tree.java
+ * Created Time: 2022-12-10
+ * Author: Krahets (krahets@163.com)
+ */
+
+ package chapter_tree;
+
+ import include.*;
+ 
+ // Tree class
+ class AVLTree {
+     TreeNode root;  // 根节点
+ 
+     /* 获取结点高度 */ 
+     public int height(TreeNode node) {
+         // 空结点高度为 -1 ，叶结点高度为 0
+         return node == null ? -1 : node.height;
+     }
+ 
+     /* 更新结点高度 */
+     private void updateHeight(TreeNode node) {
+         node.height = Math.max(height(node.left), height(node.right)) + 1;  
+     }
+ 
+     /* 获取平衡因子 */ 
+     public int balanceFactor(TreeNode node) {
+         if (node == null)
+             return 0;
+         return height(node.left) - height(node.right);
+     }
+ 
+     /* 右旋操作 */ 
+     private TreeNode rightRotate(TreeNode node) {
+         TreeNode child = node.left;
+         TreeNode grandChild = child.right;
+         child.right = node;
+         node.left = grandChild;
+         updateHeight(node);
+         updateHeight(child);
+         return child;
+     }
+ 
+     /* 左旋操作 */ 
+     private TreeNode leftRotate(TreeNode node) {
+         TreeNode child = node.right;
+         TreeNode grandChild = child.left;
+         child.left = node;
+         node.right = grandChild;
+         updateHeight(node);
+         updateHeight(child);
+         return child;
+     }
+ 
+     /* 执行旋转操作，使该子树重新恢复平衡 */
+     private TreeNode rotate(TreeNode node) {
+         int balanceFactor = balanceFactor(node);
+         // 根据失衡情况分为四种操作：右旋、左旋、先左后右、先右后左
+         if (balanceFactor > 1) {
+             if (balanceFactor(node.left) >= 0) {
+                 // 右旋
+                 return rightRotate(node);
+             } else {
+                 // 先左旋后右旋
+                 node.left = leftRotate(node.left);
+                 return rightRotate(node);
+             }
+         }
+         if (balanceFactor < -1) {
+             if (balanceFactor(node.right) <= 0) {
+                 // 左旋
+                 return leftRotate(node);
+             } else {
+                 // 先右旋后左旋
+                 node.right = rightRotate(node.right);
+                 return leftRotate(node);
+             }
+         }
+         return node;
+     }
+ 
+     /* 插入结点 */
+     public TreeNode insert(int val) {
+         root = insertHelper(root, val);
+         return root;
+     }
+ 
+     /* 递归插入结点 */
+     private TreeNode insertHelper(TreeNode node, int val) {
+         // 1. 查找插入位置，并插入结点
+         if (node == null)
+             return new TreeNode(val);
+         if (val < node.val)
+             node.left = insertHelper(node.left, val);
+         else if (val > node.val)
+             node.right = insertHelper(node.right, val);
+         else
+             return node;  // 重复结点则直接返回
+         // 2. 更新结点高度
+         updateHeight(node);
+         // 3. 执行旋转操作，使该子树重新恢复平衡
+         node = rotate(node);
+         // 返回该子树的根节点
+         return node;
+     }
+ 
+     /* 删除结点 */
+     public TreeNode remove(int val) {
+         root = removeHelper(root, val);
+         return root;
+     }
+ 
+     /* 递归删除结点 */
+     private TreeNode removeHelper(TreeNode node, int val) {
+         // 1. 查找结点，并删除之
+         if (node == null)
+             return null;
+         if (val < node.val)
+             node.left = removeHelper(node.left, val);
+         else if (val > node.val)
+             node.right = removeHelper(node.right, val);
+         else {
+             if (node.left == null || node.right == null) {
+                 TreeNode child = node.left != null ? node.left : node.right;
+                 // 子结点数量 = 0 ，直接删除 node 并返回
+                 if (child == null)
+                     return null;
+                 // 子结点数量 = 1 ，直接删除 node
+                 else
+                     node = child;
+             } else {
+                 // 子结点数量 = 2 ，则将中序遍历的下个结点删除，并用该结点替换当前结点
+                 TreeNode temp = minNode(node.right);
+                 node.right = removeHelper(node.right, temp.val);
+                 node.val = temp.val;
+             }
+         }
+         // 2. 更新结点高度
+         updateHeight(node);
+         // 3. 执行旋转操作，使该子树重新恢复平衡
+         node = rotate(node);
+         // 返回该子树的根节点
+         return node;
+     }
+ 
+     /* 获取最小结点 */
+     private TreeNode minNode(TreeNode node) {
+         if (node == null) return node;
+         // 循环访问左子结点，直到叶结点时为最小结点，跳出
+         while (node.left != null) {
+             node = node.left;
+         }
+         return node;
+     }
+ 
+     /* 查找结点 */
+     public TreeNode search(int val) {
+         TreeNode cur = root;
+         // 循环查找，越过叶结点后跳出
+         while (cur != null) {
+             // 目标结点在 root 的右子树中
+             if (cur.val < val) cur = cur.right;
+             // 目标结点在 root 的左子树中
+             else if (cur.val > val) cur = cur.left;
+             // 找到目标结点，跳出循环
+             else break;
+         }
+         // 返回目标结点
+         return cur;
+     }
+ }
+ 
+ 
+ public class avl_tree {
+     static void testInsert(AVLTree tree, int val) {
+         tree.insert(val);
+         System.out.println("\n插入结点 " + val + " 后，AVL 树为");
+         PrintUtil.printTree(tree.root);
+     }
+ 
+     static void testRemove(AVLTree tree, int val) {
+         tree.remove(val);
+         System.out.println("\n删除结点 " + val + " 后，AVL 树为");
+         PrintUtil.printTree(tree.root);
+     }
+ 
+     public static void main(String[] args) {
+         /* 初始化空 AVL 树 */
+         AVLTree avlTree = new AVLTree();
+ 
+         /* 插入结点 */
+         // 请关注插入结点后，AVL 树是如何保持平衡的
+         testInsert(avlTree, 1);
+         testInsert(avlTree, 2);
+         testInsert(avlTree, 3);
+         testInsert(avlTree, 4);
+         testInsert(avlTree, 5);
+         testInsert(avlTree, 8);
+         testInsert(avlTree, 7);
+         testInsert(avlTree, 9);
+         testInsert(avlTree, 10);
+         testInsert(avlTree, 6);
+ 
+         /* 插入重复结点 */
+         testInsert(avlTree, 7);
+ 
+         /* 删除结点 */
+         // 请关注删除结点后，AVL 树是如何保持平衡的
+         testRemove(avlTree, 8);  // 删除度为 0 的结点
+         testRemove(avlTree, 5);  // 删除度为 1 的结点
+         testRemove(avlTree, 4);  // 删除度为 2 的结点
+ 
+         /* 查询结点 */
+         TreeNode node = avlTree.search(7);
+         System.out.println("\n查找到的结点对象为 " + node + "，结点值 = " + node.val);
+     }
+ }
+ 
\ No newline at end of file
diff --git a/codes/java/include/TreeNode.java b/codes/java/include/TreeNode.java
index 6541064..98b9f82 100755
--- a/codes/java/include/TreeNode.java
+++ b/codes/java/include/TreeNode.java
@@ -12,9 +12,10 @@ import java.util.*;
  * Definition for a binary tree node.
  */
 public class TreeNode {
-    public int val;
-    public TreeNode left;
-    public TreeNode right;
+    public int val;        // 结点值
+    public int height;     // 结点高度
+    public TreeNode left;  // 左子结点引用
+    public TreeNode right; // 右子结点引用
 
     public TreeNode(int x) {
         val = x;