title: How to use a void method in a Java Reactor chain?
body: <p>Consider this code:</p>
  
  <pre><code>import reactor.core.publisher.Mono;
  
  public class Main {
  
      public static void main(String[] args) {
          Mono.just(1)
              .map(Main::return_int) // is ok
  //          .map(Main::return_void) // is not ok
              .subscribe();
      }
  
      private static void return_void(int input) {
          // do stuff with input
      }
  
      private static int return_int(int input) {
          return input;
      }
  }
  </code></pre>
  
  <p>Obviously it's forbidden to use <code>Mono#map</code> with a void param, I get <code>error: method map in class Mono&lt;T&gt; cannot be applied to given types; (...)</code></p>
  
  <p>Now how can I call this method <code>return_void()</code> in a chain ?</p>
  
  <p>Should I use another operator than <code>#map</code>? Or is there no other choice than wrapping <code>return_void()</code> into a method that returns <code>Mono&lt; Void&gt;</code> ?</p>