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

*** 495,504 ****
--- 495,505 ----
          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();
*** 3227,3236 ****
--- 3228,3238 ----
      }
  
      /**
       * 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());