title: getSource in Java gets error
body: <p>My project JavaBasic gets <code>NullPointerException</code> at this line :</p>
  
  <pre><code>url = this.getClass().getClassLoader().getResource("/JavaBasic/res/sfx_wing.wav");
  </code></pre>
  
  <p>I think my getResource method get problems and it's relevant to Classpath, how can I set it ? Thanks!</p>