diff --git a/src/main/java/xyz/zhouxy/plusone/validator/StringValidator.java b/src/main/java/xyz/zhouxy/plusone/validator/StringValidator.java
index f1676b0..d601241 100644
--- a/src/main/java/xyz/zhouxy/plusone/validator/StringValidator.java
+++ b/src/main/java/xyz/zhouxy/plusone/validator/StringValidator.java
@@ -2,6 +2,7 @@ package xyz.zhouxy.plusone.validator;
 
 import java.util.Collection;
 import java.util.List;
+import java.util.Objects;
 import java.util.function.Function;
 import java.util.function.Supplier;
 import java.util.regex.Pattern;