public static void main()

in mqtt-example/src/main/java/org/apache/rocketmq/mqtt/example/MqttWillRetainProducer.java [36:90]
50 lines of code
2 McCabe index (conditional complexity)

    public static void main(String[] args) throws InterruptedException, MqttException, NoSuchAlgorithmException, InvalidKeyException {
        MemoryPersistence memoryPersistence = new MemoryPersistence();
        String brokerUrl = "tcp://" + System.getenv("host") + ":1883";
        String firstTopic = System.getenv("topic");
        String sendClientId = "send02";
        MqttConnectOptions mqttConnectOptions = buildMqttConnectOptions(sendClientId);
        mqttConnectOptions.setWill(firstTopic + "/willTopic1", "will message: hello".getBytes(), 1, false);

        MqttClient mqttClient = new MqttClient(brokerUrl, sendClientId, memoryPersistence);
        mqttClient.setTimeToWait(5000L);
        mqttClient.setCallback(new MqttCallbackExtended() {
            @Override
            public void connectComplete(boolean reconnect, String serverURI) {
                System.out.println(sendClientId + " connect success to " + serverURI);
            }

            @Override
            public void connectionLost(Throwable throwable) {
                throwable.printStackTrace();
            }

            @Override
            public void messageArrived(String topic, MqttMessage mqttMessage) {
            }

            @Override
            public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
            }
        });
        try {
            mqttClient.connect(mqttConnectOptions);
        } catch (Exception e) {
            e.printStackTrace();
        }
        String msg = "r_" + System.currentTimeMillis();
        MqttMessage message = new MqttMessage(msg.getBytes(StandardCharsets.UTF_8));
        message.setQos(1);
        message.setRetained(true);
        String mqttSendTopic = firstTopic + "/retainTopicR";
        mqttClient.publish(mqttSendTopic, message);
        System.out.println(now() + "send: " + mqttSendTopic + ", " + msg);
        Thread.sleep(1000);
        message = new MqttMessage(msg.getBytes(StandardCharsets.UTF_8));
        message.setQos(1);
        message.setRetained(true);
        mqttSendTopic = firstTopic + "/retainTopic/wc";
        mqttClient.publish(mqttSendTopic, message);
        System.out.println(now() + "send: " + mqttSendTopic + ", " + msg);

        message = new MqttMessage();
        message.setQos(1);
        message.setRetained(true);
        mqttSendTopic = firstTopic + "/retainTopic/2";
        mqttClient.publish(mqttSendTopic, message);
    }