title: Performance for Java Stream.concat VS Collection.addAll
body: <p>For the purpose of combining two sets of data in a stream.</p>
  
  <pre><code>Stream.concat(stream1, stream2).collect(Collectors.toSet());
  </code></pre>
  
  <p>Or </p>
  
  <pre><code>stream1.collect(Collectors.toSet())
         .addAll(stream2.collect(Collectors.toSet()));
  </code></pre>
  
  <p>Which is more efficient and why?</p>