diff --git a/core-java-modules/core-java-string-operations-3/src/main/java/com/baeldung/stringfilenamevalidaiton/StringFilenameValidationUtils.java b/core-java-modules/core-java-string-operations-3/src/main/java/com/baeldung/stringfilenamevalidaiton/StringFilenameValidationUtils.java
index 6721d52d35..6cb4d3c141 100644
--- a/core-java-modules/core-java-string-operations-3/src/main/java/com/baeldung/stringfilenamevalidaiton/StringFilenameValidationUtils.java
+++ b/core-java-modules/core-java-string-operations-3/src/main/java/com/baeldung/stringfilenamevalidaiton/StringFilenameValidationUtils.java
@@ -10,7 +10,7 @@ public class StringFilenameValidationUtils {
     public static final Character[] INVALID_WINDOWS_SPECIFIC_CHARS = {'"', '*', '<', '>', '?', '|'};
     public static final Character[] INVALID_UNIX_SPECIFIC_CHARS = {'\000'};
 
-    public static final String REGEX_PATTERN = "^[A-za-z0-9.]{1,255}$";
+    public static final String REGEX_PATTERN = "^[A-Za-z0-9.]{1,255}$";
 
     private StringFilenameValidationUtils() {
     }