--- a/src/java.base/share/classes/java/util/GregorianCalendar.java	Thu Aug 29 18:52:30 2019 -0400
+++ b/src/java.base/share/classes/java/util/GregorianCalendar.java	Thu Aug 29 16:31:34 2019 -0700
@@ -497,6 +497,7 @@
 
     // Proclaim serialization compatibility with JDK 1.1
     @SuppressWarnings("FieldNameHidesFieldInSuperclass")
+    @java.io.Serial
     static final long serialVersionUID = -8125100834729963327L;
 
     // Reference to the sun.util.calendar.Gregorian instance (singleton).
@@ -3229,6 +3230,7 @@
     /**
      * Updates internal state.
      */
+    @java.io.Serial
     private void readObject(ObjectInputStream stream)
             throws IOException, ClassNotFoundException {
         stream.defaultReadObject();