src/java.base/share/classes/java/time/ZonedDateTime.java

*** 165,174 ****
--- 165,175 ----
          implements Temporal, ChronoZonedDateTime<LocalDate>, Serializable {
  
      /**
       * Serialization version.
       */
+     @java.io.Serial
      private static final long serialVersionUID = -6260982410461394882L;
  
      /**
       * The local date-time.
       */
*** 2239,2258 ****
--- 2240,2261 ----
       *  // the <a href="{@docRoot}/serialized-form.html#java.time.ZoneId">zone ID</a> excluding the one byte header
       * </pre>
       *
       * @return the instance of {@code Ser}, not null
       */
+     @java.io.Serial
      private Object writeReplace() {
          return new Ser(Ser.ZONE_DATE_TIME_TYPE, this);
      }
  
      /**
       * 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");
      }
  
      void writeExternal(DataOutput out) throws IOException {