In java code show me how send message to kafka give me an example

To send a message to Kafka in Java, you can use the KafkaProducer class from the Kafka Clients library. Here is an example code snippet:

import org.apache.kafka.clients.producer.*;

import java.util.Properties;

public class KafkaProducerExample {

    public static void main(String[] args) {

        // set up the producer properties
        Properties props = new Properties();
        props.put("bootstrap.servers", "localhost:9092");
        props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

        // create a KafkaProducer instance
        Producer<String, String> producer = new KafkaProducer<>(props);

        // create a message to send
        String topic = "my-topic";
        String key = "my-key";
        String value = "Hello, Kafka!";

        // create a ProducerRecord instance with the topic, key, and value
        ProducerRecord<String, String> record = new ProducerRecord<>(topic, key, value);

        // send the message
        producer.send(record);

        // close the producer
        producer.close();
    }
}

In this example, we first set up the producer properties, including the Kafka broker address, key and value serializers. Then, we create a KafkaProducer instance with these properties. Next, we create a message to send, consisting of a topic, key, and value. We use these to create a ProducerRecord instance. Finally, we call the send() method on the producer instance to send the message, and close the producer