title: Implementing interfaces in Kotlin
body: <p>could anyone explain to me the syntax of this interface implementation?
  Why I need to use the sign '=' to implement CommandLineRunner. When I use sign ':'(accord to basic syntax <a href="http://kotlinlang.org/docs/reference/interfaces.html" rel="nofollow noreferrer">http://kotlinlang.org/docs/reference/interfaces.html</a>) compiler requires a return statement.</p>
  
  <pre><code>@SpringBootApplication 
   class Application{
  
  @Bean
  fun imageProcess(repo: MongoRepository) = CommandLineRunner {      
     val room2 = Room(id ="1AN1",
                      primaryUnit = "XYZ")
      repo.save(room)}}
  
  @FunctionalInterface
  public interface CommandLineRunner {
  void run(String... args) throws Exception;}
  </code></pre>