title: CompletionStage, CompletableFuture Void - what to return?
body: <p>Here is my method :</p>
  
  <pre><code>public CompletionStage&lt;Void&gt; insert(List&lt;HashAction&gt; hashActionList) {
      if(!hashActionList.isEmpty()) {
          return ...
      }
      // what to return here ?
  }
  </code></pre>
  
  <p>I have no idea of what to return if my list is empty. Not sure that null is good since I would have to check for null afterwards.</p>
  
  <p>I tried</p>
  
  <pre><code>return CompletableFuture.completedFuture(null);
  </code></pre>
  
  <p>But I'm not really convinced since I chose randomly one implementation of CompletionStage</p>