src/java.base/share/classes/java/text/DateFormat.java

*** 296,305 ****
--- 296,306 ----
       * Used in FieldPosition of date/time formatting.
       */
      public static final int TIMEZONE_FIELD = 17;
  
      // Proclaim serial compatibility with 1.1 FCS
+     @java.io.Serial
      private static final long serialVersionUID = 7218322306649953788L;
  
      /**
       * Formats the given {@code Object} into a date-time string. The formatted
       * string is appended to the given {@code StringBuffer}.
*** 864,873 ****
--- 865,875 ----
       * @see java.util.Calendar
       */
      public static class Field extends Format.Field {
  
          // Proclaim serial compatibility with 1.4 FCS
+         @java.io.Serial
          private static final long serialVersionUID = 7441350119349544720L;
  
          // table of all instances in this class, used by readResolve
          private static final Map<String, Field> instanceMap = new HashMap<>(18);
          // Maps from Calendar constant (such as Calendar.ERA) to Field
*** 941,950 ****
--- 943,953 ----
           * @throws InvalidObjectException if the constant could not be
           *         resolved.
           * @return resolved DateFormat.Field constant
           */
          @Override
+         @java.io.Serial
          protected Object readResolve() throws InvalidObjectException {
              if (this.getClass() != DateFormat.Field.class) {
                  throw new InvalidObjectException("subclass didn't correctly implement readResolve");
              }