Paho mqtt, how to implement receiving from a broker?

Question

Java

I wrote a program that sends messages from the client to the broker, but I need to write a program that will receive messages from the broker.
An example of sending a message is below:

public class MqttPublishSample {
    private String topic = "Lesson_MQTT_server";
    private String content = "Lesson message";
    private String clientId = "random id";
    private String broker = "tcp://m15.cloudmqtt.com:18594";
    private char [] password = "******".toCharArray();
    private String userName = "*****";
    private int qos = 2; // Max quality
    
    private MemoryPersistence persistence;// wtf???
    
    private void MqttMessage (String message) {
        System.out.println (message);
    }
    
    public MqttPublishSample () {
        try {
            persistence = new MemoryPersistence ();
            
            MqttMessage ("Create client");
            MqttClient client = new MqttClient (broker, clientId, persistence);
            
            MqttMessage ("Create setting of connection");
            MqttConnectOptions options = new MqttConnectOptions ();
            options.setCleanSession(true);
            options.setUserName(userName);
            options.setPassword(password);
            
            MqttMessage ("Connect to server");
            client.connect(options);
            if (client.isConnected())
                MqttMessage ("Connect is succeful!");
            else
                MqttMessage ("Connect falls");
            
            MqttMessage("Publish message");
            MqttMessage message = new MqttMessage (content.getBytes());
            message.setQos(qos);
            client.publish(topic, message);
            MqttMessage("Message was published!");
            
            client.disconnect();
            MqttMessage("Disconnect!");
            
        } catch (MqttException ex) {
            System.out.println("reason: " + ex.getReasonCode());
            System.out.println("msg: " + ex.getMessage());
            System.out.println("loc : " + ex.getLocalizedMessage());
            System.out.println("cause: " + ex.getCause());
        }
    }
    
    
    public static void main (String...strings) {
        new MqttPublishSample ();
    }
 
}