修改login,register逻辑

Change-Id: If07481bce426e50165c4005416fa9911b218aee4
diff --git a/src/main/java/database/Database2.java b/src/main/java/database/Database2.java
index 5152e47..d2d98c7 100644
--- a/src/main/java/database/Database2.java
+++ b/src/main/java/database/Database2.java
@@ -53,6 +53,11 @@
     }
 
     @Override
+    public String LoginUser(User userinfo){
+        return null;
+    }
+
+    @Override
     public int RegisterUser(User userinfo) {
         return 0;
     }