<!-- in your <dependencies> block -->
  <dependency>
      <groupId>org.apache.rocketmq</groupId>
      <artifactId>rocketmq-client</artifactId>
      <version>4.9.4</version>
  </dependency>
  
  <dependency>
      <groupId>org.apache.rocketmq</groupId>
      <artifactId>rocketmq-acl</artifactId>
      <version>4.9.4</version>
  </dependency>

// Instantiate a message producer.
   DefaultMQProducer producer = new DefaultMQProducer(
       groupName,
       new AclClientRPCHook(new SessionCredentials(accessKey, secretKey)) // ACL permissions.
   );
   // Set the NameServer address.
   producer.setNamesrvAddr(nameserver);
   // Start the producer instance.
   producer.start();


int totalMessagesToSend = 1;
for (int i = 0; i < totalMessagesToSend; i++) {    
    Message message = new Message(TOPIC_NAME, ("Hello timer message " + i).getBytes());    
    // Set the time for sending a message.    
    long timeStamp = System.currentTimeMillis() + 30000;    
    // To send a scheduled message, specify the scheduled delivery time. The message will be delivered at the specified time. For example, the message will be delivered at 08:08:08 on August 8, 2022.    
    // If the specified timestamp is earlier than the current time, the message will be delivered to the consumer immediately.    
    //Set __STARTDELIVERTIME into the message properties.    
    message.putUserProperty("__STARTDELIVERTIME", String.valueOf(timeStamp));    
    // Send messages.    
    SendResult sendResult = producer.send(message);    
    System.out.println("sendResult = " + sendResult);
}

// Instantiate a consumer.
        DefaultMQPushConsumer pushConsumer = new DefaultMQPushConsumer(
            groupName,                                              
            new AclClientRPCHook(new SessionCredentials(accessKey, secretKey))); // ACL permissions.
        // Set the NameServer address.
        pushConsumer.setNamesrvAddr(nameserver);

// Subscribe to a topic.
      pushConsumer.subscribe(topic_name, "*");
      // Register a callback implementation class to handle messages pulled from the broker.
      pushConsumer.registerMessageListener((MessageListenerConcurrently) (msgs, context) -> {
          // Message processing logic.
          System.out.printf("%s Receive New Messages: %s %n", Thread.currentThread().getName(), msgs);
          // Mark the message as successfully consumed and return an appropriate status.
          return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
      });
      // Start the consumer instance.
      pushConsumer.start();