diff --git a/problems/0098.验证二叉搜索树.md b/problems/0098.验证二叉搜索树.md
index ddd634b4..336cc92f 100644
--- a/problems/0098.验证二叉搜索树.md
+++ b/problems/0098.验证二叉搜索树.md
@@ -254,7 +254,56 @@ public:
 
 
 Java：
+```Java
+class Solution {
+    // 递归
+    TreeNode max;
+    public boolean isValidBST(TreeNode root) {
+        if (root == null) {
+            return true;
+        }
+        // 左
+        boolean left = isValidBST(root.left);
+        if (!left) {
+            return false;
+        }
+        // 中
+        if (max != null && root.val <= max.val) {
+            return false;
+        }
+        max = root;
+        // 右
+        boolean right = isValidBST(root.right);
+        return right;
+    }
+}
 
+class Solution {
+    // 迭代
+    public boolean isValidBST(TreeNode root) {
+        if (root == null) {
+            return true;
+        }
+        Stack<TreeNode> stack = new Stack<>();
+        TreeNode pre = null;
+        while (root != null || !stack.isEmpty()) {
+            while (root != null) {
+                stack.push(root);
+                root = root.left;// 左
+            }
+            // 中，处理
+            TreeNode pop = stack.pop();
+            if (pre != null && pop.val <= pre.val) {
+                return false;
+            }
+            pre = pop;
+
+            root = pop.right;// 右
+        }
+        return true;
+    }
+}
+```
 
 Python：