--- old/src/java.base/share/classes/java/util/DuplicateFormatFlagsException.java	2019-08-27 17:28:53.394324386 -0700
+++ new/src/java.base/share/classes/java/util/DuplicateFormatFlagsException.java	2019-08-27 17:28:53.210324386 -0700
@@ -37,6 +37,7 @@
  */
 public class DuplicateFormatFlagsException extends IllegalFormatException {
 
+    @java.io.Serial
     private static final long serialVersionUID = 18890531L;
 
     private String flags;