如何将字符串词添加到Kstream<String，String>？

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.Properties;

public class StringWordAdder {
    public static void main(String[] args) {
        // 设置Kafka Streams配置
        Properties props = new Properties();
        props.put(StreamsConfig.APPLICATION_ID_CONFIG, "string-word-adder");
        props.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");

        // 创建流构建器
        StreamsBuilder builder = new StreamsBuilder();

        // 创建输入流
        KStream<String, String> inputStream = builder.stream("input-topic");

        // 对每个记录的值进行转换操作，将字符串词添加到值中
        KStream<String, String> outputStream = inputStream.mapValues(value -> value + " word");

        // 将结果写入输出流
        outputStream.to("output-topic");

        // 构建Kafka Streams对象并启动
        KafkaStreams streams = new KafkaStreams(builder.build(), props);
        streams.start();

        // 添加关闭钩子，确保在应用程序关闭时关闭Kafka Streams
        Runtime.getRuntime().addShutdownHook(new Thread(streams::close));
    }
}