diff --git a/src/main/java/org/wlld/randomForest/Tree.java b/src/main/java/org/wlld/randomForest/Tree.java
index fc83861..1d1f5f0 100644
--- a/src/main/java/org/wlld/randomForest/Tree.java
+++ b/src/main/java/org/wlld/randomForest/Tree.java
@@ -13,7 +13,7 @@ import java.util.*;
 public class Tree {//决策树
     private DataTable dataTable;
     private Map<String, List<Integer>> table;//总样本
-    private Node rootNode = new Node();//根节点
+    private Node rootNode;//根节点
     private List<Integer> endList;//最终结果分类
     private List<Node> lastNodes = new ArrayList<>();//最后一层节点集合
     private Random random = new Random();
@@ -203,7 +203,11 @@ public class Tree {//决策树
     }
 
     public int judge(Object ob) throws Exception {//进行类别判断
-        return goTree(ob, rootNode);
+        if (rootNode != null) {
+            return goTree(ob, rootNode);
+        } else {
+            throw new Exception("rootNode is null");
+        }
     }
 
     private int goTree(Object ob, Node node) throws Exception {//从树顶向下攀爬
@@ -230,6 +234,7 @@ public class Tree {//决策树
 
     public void study() throws Exception {
         if (dataTable != null && dataTable.getLength() > 0) {
+            rootNode = new Node();
             table = dataTable.getTable();
             endList = dataTable.getTable().get(dataTable.getKey());
             Set<String> set = dataTable.getKeyType();