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

@@ -296,10 +296,11 @@
      * 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}.

@@ -864,10 +865,11 @@
      * @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

@@ -941,10 +943,11 @@
          * @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");
             }