title: stream() vs. parallelStream() when adding in an ArrayList
body: <p>I had this piece of code</p>
  
  <pre><code>List&lt;UserNotification&gt; userNotifications = new ArrayList&lt;UserNotification&gt;();
  
  teatreAlertNotifications
              .parallelStream()
              .forEach(can -&gt; userNotifications.add(new UserNotification(can)));
  </code></pre>
  
  <p>But since ArrayList is unsynchronized I think it is  bad practice and I should use .stream() instead</p>