src/java.base/share/classes/java/time/chrono/IsoChronology.java

@@ -131,10 +131,11 @@
     public static final IsoChronology INSTANCE = new IsoChronology();
 
     /**
      * Serialization version.
      */
+    @java.io.Serial
     private static final long serialVersionUID = -1440403870442975015L;
 
     private static final long DAYS_0000_TO_1970 = (146097 * 5L) - (30L * 365L + 7L); // taken from LocalDate
 
     /**

@@ -687,19 +688,21 @@
      * </pre>
      *
      * @return the instance of {@code Ser}, not null
      */
     @Override
+    @java.io.Serial
     Object writeReplace() {
         return super.writeReplace();
     }
 
     /**
      * 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");
     }
 }