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

*** 141,150 ****
--- 141,151 ----
       */
      private static final int MAX_SECONDS = 18 * SECONDS_PER_HOUR;
      /**
       * Serialization version.
       */
+     @java.io.Serial
      private static final long serialVersionUID = 2357656521762053153L;
  
      /**
       * The time-zone offset for UTC, with an ID of 'Z'.
       */
*** 761,780 ****
--- 762,783 ----
       *  }
       * </pre>
       *
       * @return the instance of {@code Ser}, not null
       */
+     @java.io.Serial
      private Object writeReplace() {
          return new Ser(Ser.ZONE_OFFSET_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");
      }
  
      @Override