src/java.base/share/classes/java/time/chrono/IsoChronology.java

*** 131,140 ****
--- 131,141 ----
      public static final IsoChronology INSTANCE = new IsoChronology();
  
      /**
       * Serialization version.
       */
+     @java.io.Serial
      private static final long serialVersionUID = -1440403870442975015L;
  
      private static final long DAYS_0000_TO_1970 = (146097 * 5L) - (30L * 365L + 7L); // taken from LocalDate
  
      /**
*** 687,705 ****
--- 688,708 ----
       * </pre>
       *
       * @return the instance of {@code Ser}, not null
       */
      @Override
+     @java.io.Serial
      Object writeReplace() {
          return super.writeReplace();
      }
  
      /**
       * Defend against malicious streams.
       *
       * @param s the stream to read
       * @throws InvalidObjectException always
       */
+     @java.io.Serial
      private void readObject(ObjectInputStream s) throws InvalidObjectException {
          throw new InvalidObjectException("Deserialization via serialization delegate");
      }
  }