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

*** 90,99 ****
--- 90,100 ----
  final class ZoneRegion extends ZoneId implements Serializable {
  
      /**
       * Serialization version.
       */
+     @java.io.Serial
      private static final long serialVersionUID = 8386373296231747096L;
      /**
       * The time-zone ID, not null.
       */
      private final String id;
*** 187,206 ****
--- 188,209 ----
       *  out.writeUTF(zoneId);
       * </pre>
       *
       * @return the instance of {@code Ser}, not null
       */
+     @java.io.Serial
      private Object writeReplace() {
          return new Ser(Ser.ZONE_REGION_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