code: private static File _getClassSource (final String className)
    {
      if (className != null)
      {
        final String classResource = className.replace ('.', '/') + ".class";
        return _getResourceSource (classResource, Thread.currentThread ().getContextClassLoader ());
      }
      return null;
    }
docs: Gets the JAR file or directory that contains the specified class.
  
  @param className
  The qualified name of the class/interface to find, may be
  <code>null</code>.
  @return The absolute path to the class source location or <code>null</code>
  if unknown.