diff --git a/backend/src/main/java/ervu_business_metrics/security/service/ErvuJwtTokenService.java b/backend/src/main/java/ervu_business_metrics/security/service/ErvuJwtTokenService.java
index d89c0fd..661388c 100644
--- a/backend/src/main/java/ervu_business_metrics/security/service/ErvuJwtTokenService.java
+++ b/backend/src/main/java/ervu_business_metrics/security/service/ErvuJwtTokenService.java
@@ -2,7 +2,11 @@ package ervu_business_metrics.security.service;
 
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Base64;
+import java.util.Date;
+import java.util.List;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 import javax.crypto.SecretKey;