Update java/food-ordering/app/restate-app/src/main/java/dev/restate/s…

…dk/examples/clients/KafkaPublisher.java

Co-authored-by: Francesco Guardiani <francescoguard@gmail.com>

java/food-ordering/app/restate-app/src/main/java/dev/restate/sdk/examples/clients/KafkaPublisher.java

@@ -14,7 +14,7 @@ public class KafkaPublisher {
           ? System.getenv("KAFKA_BOOTSTRAP_SERVERS")
           : "127.0.0.1:9092";
 
-  KafkaProducer<String, byte[]> producer;
+  private final KafkaProducer<String, byte[]> producer;
 
   public KafkaPublisher() {
     this.producer = new KafkaProducer<>(properties());