code: public void setOutputDirectory (final File directory)
    {
      if (directory != null && !directory.isAbsolute ())
      {
        throw new IllegalArgumentException ("output directory is not absolute: " + directory);
      }
      this.outputDirectory = directory;
    }
docs: Sets the absolute path to the output directory used to detect stale target
  files.
  
  @param directory
  The absolute path to the output directory used to detect stale target
  files by timestamp checking, may be <code>null</code> if no stale
  detection should be performed.