Kafka consumer showing numbers in unreadable format

I am trying out the kafka streaming. I am reading messages from one topic and doing groupByKey and then doing the count of groups. But the problem is that the messages count is coming as unreadable "boxes".

If I run the console consumer these are coming as empty strings

This is the WordCount code I wrote

package streams;
import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.common.serialization.Serdes;
import org.apache.kafka.streams.KafkaStreams;
import org.apache.kafka.streams.StreamsBuilder;
import org.apache.kafka.streams.StreamsConfig;
import org.apache.kafka.streams.kstream.KStream;
import java.util.Arrays;
import java.util.Properties;
public class WordCount {
public static void main(String[] args) {
Properties properties = new Properties();
properties.setProperty(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
properties.setProperty(StreamsConfig.APPLICATION_ID_CONFIG, "streams-demo-2");
properties.setProperty(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
properties.setProperty(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.StringSerde.class.getName());
properties.setProperty(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.StringSerde.class.getName());
// topology
StreamsBuilder builder = new StreamsBuilder();
KStream<String, String> input = builder.stream("temp-in");
KStream<String, Long> fil = input.flatMapValues(val -> Arrays.asList(val.split(" "))) // making stream of text line to stream of words
.selectKey((k, v) -> v) // changing the key
.groupByKey().count().toStream(); // getting count after groupBy
fil.to("temp-out");
KafkaStreams streams = new KafkaStreams(builder.build(), properties);
streams.start();
System.out.println(streams.toString());
Runtime.getRuntime().addShutdownHook(new Thread(streams::close));
}
}

This is the output I am getting in the consumer. It is there on the right side in image

I had tried casting the long to long again to see if it works. But it's not working

I am attaching the consumer code too if it helps.

package tutorial;
import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.common.serialization.StringDeserializer;
import java.time.Duration;
import java.util.Collections;
import java.util.Properties;
public class Consumer {
public static void main(String[] args) {
Properties properties = new Properties();
properties.setProperty(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
properties.setProperty(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
properties.setProperty(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
// Once the consumer starts running it keeps running even after we stop in console
// We should create new consumer to read from earliest because the previous one had already consumed until certain offset
// when we run the same consumer in two consoles kafka detects it and re balances
// In this case the consoles split the partitions they consume forming a consumer group
properties.setProperty(ConsumerConfig.GROUP_ID_CONFIG, "consumer-application-1"); // -> consumer id
properties.setProperty(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest"); // -> From when consumer gets data
KafkaConsumer<String, String> consumer = new KafkaConsumer<>(properties);
consumer.subscribe(Collections.singleton("temp-out"));
while (true) {
ConsumerRecords<String, String> consumerRecords = consumer.poll(Duration.ofMillis(1000));
for (ConsumerRecord<String, String> record: consumerRecords) {
System.out.println(record.key() + " " + record.value());
System.out.println(record.partition() + " " + record.offset());
}
}
}
}

Any help is appreciated. Thanks in advance.

The message value you're writing with Kafka Streams is a Long, and you're consuming it as a String.

If you make the following changes to your Consumer class, you'll be able to see the count printed correctly to stdout:

        // Change this from StringDeserializer to LongDeserializer.
properties.setProperty(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, LongDeserializer.class.getName());
...
// The value you're consuming here is a Long, not a String.
KafkaConsumer<String, Long> consumer = new KafkaConsumer<>(properties);
consumer.subscribe(Collections.singleton("temp-out"));
while (true) {
ConsumerRecords<String, Long> consumerRecords = consumer.poll(Duration.ofMillis(1000));
for (ConsumerRecord<String, Long> record : consumerRecords) {
System.out.println(record.key() + " " + record.value());
System.out.println(record.partition() + " " + record.offset());
}
}