String value = "message content";
try {
        //It is necessary to explicitly convert the desired time to a timestamp.
      long timeStamp = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse("2020-11-11 00:00:00").getTime();
      //Call the deliverAt method of the producer to implement scheduled messages.
        MessageId msgId = producer.newMessage()
                .value(value.getBytes())
                .deliverAt(timeStamp)
                .send();
} catch (ParseException e) {
        //To-do: Add a method to handle timestamp parsing failures.
        e.printStackTrace();
}

String value = "message content";

//You need to specify the delayed duration.
long delayTime = 10L;
//Call the deliverAfter method of the producer to implement scheduled messages.
MessageId msgId = producer.newMessage()
    .value(value.getBytes())
    .deliverAfter(delayTime, TimeUnit.SECONDS) //The unit can be selected freely.
    .send();