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

@@ -495,10 +495,11 @@
         2*ONE_HOUR      // DST_OFFSET (double summer time)
     };
 
     // 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).
     private static final Gregorian gcal =
                                 CalendarSystem.getGregorianCalendar();

@@ -3227,10 +3228,11 @@
     }
 
     /**
      * Updates internal state.
      */
+    @java.io.Serial
     private void readObject(ObjectInputStream stream)
             throws IOException, ClassNotFoundException {
         stream.defaultReadObject();
         if (gdate == null) {
             gdate = (BaseCalendar.Date) gcal.newCalendarDate(getZone());