title: VFY: unable to find class referenced in signature in IntelliJ IDEA
body: <p>I have a jar library in my Android project, and I'm started to get a lot of errors while running the app:</p>
  
  <pre><code>VFY: unable to find class referenced in signature &lt;...&gt;
  Failed resolving Lcom/mad/ad/AdWhirlMadAdapter; interface 835 'Lcom/adwhirl/AdWhirlLayout$AdWhirlInterface;'
  Link of class 'Lcom/mad/ad/AdWhirlMadAdapter;' failed
  </code></pre>
  
  <p>I've seen a lot of similar questions, but the solutions are for Eclipse, and I'm using IntelliJ IDEA 12. How to fix it?</p>