title: Eclipse RCP: java.lang.ClassNotFoundException a runtime
body: <p>One of my plugins uses a library (jar file).</p>
  
  <ol>
  <li>I created a folder called lib in my plugin and placed the jar file into it.</li>
  <li>I configured the build path by adding the jar file with "Add JARS..".</li>
  <li>I use the classes of the jar file in the plugin and it compiles fine.</li>
  <li>I start the RCP and get a ClassNotFoundException about the classes in the jar file.</li>
  </ol>
  
  <p>What am I missing?</p>