添加1382.将二叉搜索树变平衡java代码

problems/1382.将二叉搜索树变平衡.md

@@ -76,7 +76,31 @@ public:
 # 其他语言版本
 
 Java：
-
+```java
+class Solution {
+    ArrayList <Integer> res = new ArrayList<Integer>();
+    // 有序树转成有序数组
+    private void travesal(TreeNode cur) {
+            if (cur == null) return;
+            travesal(cur.left);
+            res.add(cur.val);
+            travesal(cur.right);
+        }
+    // 有序数组转成平衡二叉树
+    private TreeNode getTree(ArrayList <Integer> nums, int left, int right) {
+        if (left > right) return null;
+        int mid = left + (right - left) / 2;
+        TreeNode root = new TreeNode(nums.get(mid));
+        root.left = getTree(nums, left, mid - 1);
+        root.right = getTree(nums, mid + 1, right);
+        return root;
+    }
+    public TreeNode balanceBST(TreeNode root) {
+        travesal(root);
+        return getTree(res, 0, res.size() - 1);
+    }
+}
+```
 Python：
 ```python
 class Solution: