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

*** 151,160 ****
--- 151,161 ----
      public static final LocalDateTime MAX = LocalDateTime.of(LocalDate.MAX, LocalTime.MAX);
  
      /**
       * Serialization version.
       */
+     @java.io.Serial
      private static final long serialVersionUID = 6207766400415563566L;
  
      /**
       * The date part.
       */
*** 1983,2002 ****
--- 1984,2005 ----
       *  // the <a href="{@docRoot}/serialized-form.html#java.time.LocalTime">time</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.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(DataOutput out) throws IOException {