src/java.base/share/classes/java/util/DuplicateFormatFlagsException.java

@@ -35,10 +35,11 @@
  *
  * @since 1.5
  */
 public class DuplicateFormatFlagsException extends IllegalFormatException {
 
+    @java.io.Serial
     private static final long serialVersionUID = 18890531L;
 
     private String flags;
 
     /**