title: Use external class in drupal 8 module with file name and class name
body: <p>I create a module in drupal 8 .
  I want using a class in external class file .</p>
  
  <p>File name : drupal.php</p>
  
  <p>Class name : class newman{...}</p>
  
  <p>In drupal.php :</p>
  
  <pre><code>&lt;?php
  namespace Drupal\mymodulename\lib;
  class newman{
     public function new(){
         $dp = 'TEST';
         return $dp;
     }
  }
  ?&gt;
  </code></pre>
  
  <p>In my contoller :</p>
  
  <pre><code>&lt;?php
  namespace Drupal\mymodulename\Controller;
  
  use Drupal\Core\Controller\ControllerBase;
  use Drupal\mymodulename\lib\drupal;
  
  class mmController extends ControllerBase {
      public function man() {
            $this-&gt;man=new newman();
            $build['test'] = [
                              '#markup' =&gt; $man-&gt;new(),
                             ];
      }
  }
  </code></pre>
  
  <p>Error: Class 'Drupal\mymodulename\Controller\newman' not found in Drupal...</p>
  
  <p>How can I fix it ?</p>