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

@@ -243,10 +243,11 @@
     public static final Instant MAX = Instant.ofEpochSecond(MAX_SECOND, 999_999_999);
 
     /**
      * Serialization version.
      */
+    @java.io.Serial
     private static final long serialVersionUID = -665713676816604388L;
 
     /**
      * The number of seconds from the epoch of 1970-01-01T00:00:00Z.
      */

@@ -1340,20 +1341,22 @@
      *  out.writeInt(nanos);
      * </pre>
      *
      * @return the instance of {@code Ser}, not null
      */
+    @java.io.Serial
     private Object writeReplace() {
         return new Ser(Ser.INSTANT_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 {