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

@@ -128,10 +128,11 @@
         implements TemporalAccessor, TemporalAdjuster, Comparable<MonthDay>, Serializable {
 
     /**
      * Serialization version.
      */
+    @java.io.Serial
     private static final long serialVersionUID = -939150713474957432L;
     /**
      * Parser.
      */
     private static final DateTimeFormatter PARSER = new DateTimeFormatterBuilder()

@@ -762,20 +763,22 @@
      *  out.writeByte(day);
      * </pre>
      *
      * @return the instance of {@code Ser}, not null
      */
+    @java.io.Serial
     private Object writeReplace() {
         return new Ser(Ser.MONTH_DAY_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 {