title: Strange "java.lang.NoClassDefFoundError" in Eclipse
body: <p>I have a Java project in Eclipse perfectly running smoothly until this afternoon, when I updated some files (including a ant build.xml file). When I build the project, the following error appears:</p>
  
  <pre><code>java.lang.NoClassDefFoundError: proj/absa/FrontEnd/ApplicationStarter
  Caused by: java.lang.ClassNotFoundException: proj.absa.FrontEnd.ApplicationStarter
      at java.net.URLClassLoader$1.run(Unknown Source)
      at java.security.AccessController.doPrivileged(Native Method)
      at java.net.URLClassLoader.findClass(Unknown Source) at
      java.lang.ClassLoader.loadClass(Unknown Source)
      at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
      at java.lang.ClassLoader.loadClass(Unknown Source)  
  Exception in thread "main" 
  </code></pre>
  
  <p>Does anyone have a clue where the problem may be?</p>