To build a JAR that we can run from the command line, first run: 
gradle shadowJar
And you should see the following output: 
BUILD SUCCESSFUL in 1s
Run the following command to execute the producer application, which will produce some random events to the purchases topic. 
java -cp build/libs/kafka-java-getting-started-0.0.1.jar io.streamnative.developer.ProducerExample
You should see output resembling this: 
10 events were produced to topic purchases
Produced event to topic purchases: key = awalther   value = t-shirts
Produced event to topic purchases: key = jbernard   value = alarm clock
Produced event to topic purchases: key = eabara     value = book
Produced event to topic purchases: key = htanaka    value = book
Produced event to topic purchases: key = jbernard   value = batteries
Produced event to topic purchases: key = awalther   value = book
Produced event to topic purchases: key = htanaka    value = book
Produced event to topic purchases: key = sgarcia    value = gift card
Produced event to topic purchases: key = sgarcia    value = t-shirts
Produced event to topic purchases: key = sgarcia    value = book