title: How to complete a CompletableFuture<Void>?
body: <p>I want a CompletableFuture that only signals the completion (e.g. I don't have a return value).</p>
  
  <p>I can instantiate the CompletableFuture as:</p>
  
  <pre><code>CompletableFuture&lt;Void&gt; future = new CompletableFuture&lt;&gt; ();
  </code></pre>
  
  <p>But what should I feed into the complete method? For example, I can't do </p>
  
  <pre><code>future.complete(new Void());
  </code></pre>