title: Path for retrieving resources with ClassLoader
body: <p>Basically, I want to include my main <code>JFrame</code>'s icon in the JAR file, so not to need to load it from an external location.</p>
  
  <p>To achieve this, I searched about Java's resource system.
  What I have done with Eclipse:</p>
  
  <ol>
  <li><p>I have created a new folder named "res":</p>
  
  <p><a href="https://i.stack.imgur.com/oFVGZ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/oFVGZ.png" alt=""></a></p></li>
  <li><p>I have copied the files inside it using Windows' explorer:</p>
  
  <p><a href="https://i.stack.imgur.com/nwD6L.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nwD6L.png" alt=""></a></p></li>
  <li><p>I have made that folder a source folder:</p>
  
  <p><a href="https://i.stack.imgur.com/7nN1r.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7nN1r.png" alt=""></a></p></li>
  <li><p>I have written this code:</p>
  
  <pre><code>URL url = ClassLoader.getSystemResource("/res/icona20.ico");
  </code></pre></li>
  </ol>
  
  <p>But <code>url</code> is <code>null</code>.
  What did I do wrong?</p>