diff --git a/source/graph/basic/udg/java/ListUDG.java b/source/graph/basic/udg/java/ListUDG.java
index 2ece9f3..091bdcc 100644
--- a/source/graph/basic/udg/java/ListUDG.java
+++ b/source/graph/basic/udg/java/ListUDG.java
@@ -129,12 +129,32 @@ public ListUDG(char[] vexs, char[][] edges) {
      * 将node节点链接到list的最后
      */
     private void linkLast(ENode list, ENode node) {
+        
+        // 判断list中是否有node
+        if(hasNode(list, node))
+            return;
+
+        
         ENode p = list;
 
         while(p.nextEdge!=null)
             p = p.nextEdge;
         p.nextEdge = node;
     }
+    
+    // 单链表的查询功能
+    private boolean hasNode(ENode list, ENode node) {
+        if(list == null) {
+            return false;
+        }
+
+        ENode n = list;
+        if(n.index == node.index){
+            return true;
+        }else{
+            return hasNode(n.next, node);
+        }
+    }
 
     /*
      * 返回ch位置