title: Print Kafka Stream Input out to console?
body: <p>I've been looking through a lot of the Kafka documentation for a java application that I am working on. I've tried getting into the lambda syntax introduced in Java 8, but I am a little sketchy on that ground and don't feel too confident that it should be what I use as of yet.</p>
  
  <p>I've a Kafka/Zookeeper Service running without any troubles, and what I want to do is write a small example program that based on the input will write it out, but not do a wordcount as there are so many examples of already.</p>
  
  <p>As for sample data I will be getting a string of following structure:</p>
  
  <h1>Example data</h1>
  
  <pre><code>This a sample string containing some keywords such as GPS, GEO and maybe a little bit of ACC.
  </code></pre>
  
  <h1>Question</h1>
  
  <p>I want to be able to extract the 3 letter keywords and print them with a <code>System.out.println</code>. How do I get a string variable containing the input? I know how to apply regular expressions or even just searching through the string to get the keywords.</p>
  
  <h1>Code</h1>
  
  <pre><code>public static void main(String[] args) {
      Properties props = new Properties();
      props.put(StreamsConfig.APPLICATION_ID_CONFIG, "app_id");
      props.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "0:0:0:0:0:0:0:1:9092");
      props.put(StreamsConfig.ZOOKEEPER_CONNECT_CONFIG, "0:0:0:0:0:0:0:1:2181");
      props.put(StreamsConfig.KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName());
      props.put(StreamsConfig.VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName());
  
      final Serde&lt;String&gt; stringSerde = Serdes.String();
  
      KStreamBuilder builder = new KStreamBuilder();
  
      KStream&lt;String, String&gt; source = builder.stream(stringSerde, stringSerde, "in-stream");
  
      KafkaStreams streams = new KafkaStreams(builder, props);
      streams.start();
  
      //How do I assign the input from in-stream to the following variable?
      String variable = ?
  }
  </code></pre>
  
  <p>I have zookeeper, kafka, producer and consumer running all hooked up to the same topic so I want to basically see the same <code>String</code> appear on all of the instances (producer, consumer and stream).</p>