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

*** 249,258 ****
--- 249,259 ----
          2*ONE_HOUR      // DST_OFFSET (double summer time)
      };
  
      // Proclaim serialization compatibility with JDK 1.6
      @SuppressWarnings("FieldNameHidesFieldInSuperclass")
+     @java.io.Serial
      private static final long serialVersionUID = -3364572813905467929L;
  
      static {
          Era[] es = jcal.getEras();
          int length = es.length + 1;
*** 2389,2398 ****
--- 2390,2400 ----
      }
  
      /**
       * Updates internal state.
       */
+     @java.io.Serial
      private void readObject(ObjectInputStream stream)
              throws IOException, ClassNotFoundException {
          stream.defaultReadObject();
          if (jdate == null) {
              jdate = jcal.newCalendarDate(getZone());