title: Reactor filter out Flux<String> from List<String>
body: <p>Suppose we have</p>
  <ul>
  <li><code>List&lt;String&gt; list</code> contains <code>&quot;A&quot;, &quot;B&quot;, &quot;C&quot;, &quot;D&quot;</code></li>
  <li><code>Flux&lt;String&gt; flux</code> contains <code>&quot;A&quot;, &quot;B&quot;</code></li>
  </ul>
  <p>Is there a way to filter out flux from list? In other words, subtract flux from list, where the results should be <code>&quot;C&quot;, &quot;D&quot;</code>.</p>
  <p>Looking through the documentation for reactor, <code>filterWhen</code> seems to be the closest, but it only replays the first element match the condition, all subsequent matches will be ignored.</p>
  <p>This can be easily achieved in non-reactive world, for List or Collections, e.g. <a href="https://stackoverflow.com/questions/9933403/subtracting-one-arraylist-from-another-arraylist">Subtracting one arrayList from another arrayList</a>.</p>