我是kafka的新手，我用java创建了一个示例consumer，用于从kafka主题中获取数据，但是当我使用消息时，会带来额外的字符串或字符，比如一些特殊字符（？？？？xmydata），比如这样。
如果我没有使用正确的代码，请给我提供适当的代码。

The code i am using..

        getting output = ?????mydata
        expected output = mydata 

         public static void main(String[] args) throws Exception {
                Properties props = new Properties();
                props.put("bootstrap.servers", "localhost:9092");
                props.put("group.id", "mysql-joined-datalist2");
                props.put("auto.commit.interval.ms", "1000");
                props.put("enable.auto.commit", "true");
                props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
                props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");

                //kafka consumer object
                KafkaConsumer<String, String> consumer = new KafkaConsumer<String, String>(props);

                //subscribe to topic
                consumer.subscribe(Arrays.asList("mysql-joined-datalist2"));

                //infinite poll loop
                while (true) {
                    ConsumerRecords<String, String> records = consumer.poll(0);
                    for (ConsumerRecord<String, String> record : records) {

                        String payload = record.value();
        //                InputStream is = new ByteArrayInputStream(payload.getBytes("UTF-8"));
                        String oldString = record.value();
                        String newString = new String(oldString.getBytes("UTF-8"), "UTF-8");
                        System.out.println("newString : " + newString);
                        String s2 = new String(record.value().getBytes("ISO-8859-1"),"UTF-8");
                         System.out.println("str : "+s2); // output = str : ?????Xmydata
        }

        please help me. thanks in advanced.