title: Can not include source library in project in Intellij IDEA
body: <p>I've created library project in IDEA with <strong>common helpers</strong>, which I use in my android applications. </p>
  
  <p>Then I've created android application and included in it my library project like <a href="http://www.jetbrains.com/idea/webhelp/configuring-module-dependencies-and-libraries.html" rel="nofollow noreferrer">this tutorial said</a>. </p>
  
  <p>Everything seemed okay, code autocomplete worked fine, IDEA recognize that library and all classes and methods in it. </p>
  
  <p>But then I compiled application and saw error "<strong>'org.my.helperlibrary' does not exist</strong>". However as I said IDEA acts like everything okay before making/launching project.<br></p>
  
  <p><a href="https://stackoverflow.com/questions/8884662/how-can-i-add-a-library-project-in-intellij-idea">Here is similar question</a>, but answer is trivial, of course my library has checked "<strong>Is Library Project</strong>" option but I still can not launch my application which use my library.</p>
  
  <p><strong>Updated:</strong></p>
  
  <p>I've just saw an error: "<strong>UNEXPECTED TOP-LEVEL EXCEPTION: java.lang.IllegalArgumentException: already added: Lorg/my/helperlibrary/Helper;</strong>" when I removed all usages of library in my android application. So it's just included in my app and not used.</p>