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

*** 101,110 ****
--- 101,111 ----
          implements  ChronoLocalDateTime<D>, Temporal, TemporalAdjuster, Serializable {
  
      /**
       * Serialization version.
       */
+     @java.io.Serial
      private static final long serialVersionUID = 4556003607393004514L;
      /**
       * Hours per day.
       */
      static final int HOURS_PER_DAY = 24;
*** 407,426 ****
--- 408,429 ----
       *  out.witeObject(toLocalTime());
       * </pre>
       *
       * @return the instance of {@code Ser}, not null
       */
+    @java.io.Serial
      private Object writeReplace() {
          return new Ser(Ser.CHRONO_LOCAL_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(ObjectOutput out) throws IOException {