--- cn.cloudwalk.elevator.util.StringUtils.v1
+++ cn.cloudwalk.elevator.util.StringUtils.v2
@@ -1959,6 +1959,7 @@
 Code:
 aload _
 aconst_null
+checkcast     # // class java/lang/String
 invokestatic  # // Method join:([Ljava/lang/Object;Ljava/lang/String;)Ljava/lang/String;
 areturn
 public static java.lang.String join(java.lang.Object[], char);
@@ -3993,8 +3994,8 @@
 aload _
 invokevirtual # // Method java/lang/String.length:()I
 iload _
+isub
 iconst_3
-isub
 isub
 istore _
 iload _
@@ -4021,9 +4022,9 @@
 istore _
 iload _
 iload _
+iadd
 iconst_3
 isub
-iadd
 aload _
 invokevirtual # // Method java/lang/String.length:()I
 if_icmpge @
@@ -4051,8 +4052,8 @@
 aload _
 invokevirtual # // Method java/lang/String.length:()I
 iload _
+isub
 iconst_3
-isub
 isub
 invokevirtual # // Method java/lang/String.substring:(I)Ljava/lang/String;
 invokevirtual # // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
