src/java.base/share/classes/java/util/Calendar.java

*** 1003,1012 ****
--- 1003,1013 ----
       * @since 1.1.6
       */
      private int             serialVersionOnStream = currentSerialVersion;
  
      // Proclaim serialization compatibility with JDK 1.1
+     @java.io.Serial
      static final long       serialVersionUID = -1807547505821590642L;
  
      // Mask values for calendar fields
      @SuppressWarnings("PointlessBitwiseExpression")
      static final int ERA_MASK           = (1 << ERA);
*** 3524,3533 ****
--- 3525,3535 ----
       * shipped. To be compatible with JDK 1.1, we will always have to write out
       * the field values and state flags.  However, <code>nextStamp</code> can be
       * removed from the serialization stream; this will probably happen in the
       * near future.
       */
+     @java.io.Serial
      private synchronized void writeObject(ObjectOutputStream stream)
           throws IOException
      {
          // Try to compute the time correctly, for the future (stream
          // version 2) in which we don't write out fields[] or isSet[].
*** 3578,3587 ****
--- 3580,3590 ----
      }
  
      /**
       * Reconstitutes this object from a stream (i.e., deserialize it).
       */
+     @java.io.Serial
      private void readObject(ObjectInputStream stream)
           throws IOException, ClassNotFoundException
      {
          final ObjectInputStream input = stream;
          input.defaultReadObject();