diff --git a/src/main/java/xyz/zhouxy/plusone/validator/PredicateTools.java b/src/main/java/xyz/zhouxy/plusone/validator/PredicateTools.java
index 2a06afc..b99e8cb 100644
--- a/src/main/java/xyz/zhouxy/plusone/validator/PredicateTools.java
+++ b/src/main/java/xyz/zhouxy/plusone/validator/PredicateTools.java
@@ -14,8 +14,12 @@ public class PredicateTools {
         return predicate;
     }
 
+    public static <T> boolean notNull(T obj) {
+        return obj != null;
+    }
+
     public static <T> Predicate<T> notNull() {
-        return obj -> obj != null;
+        return PredicateTools::notNull;
     }
 
     public static int length(CharSequence cs) {