code: public synchronized String[] getDeselectedFiles() {
          slowScan();
          String[] files = new String[filesDeselected.size()];
          filesDeselected.copyInto(files);
          return files;
      }
docs: <p>Return the names of the files which were selected out and
  therefore not ultimately included.</p>
  
  <p>The names are relative to the base directory. This involves
  performing a slow scan if one has not already been completed.</p>
  
  @return the names of the files which were deselected.
  
  @see #slowScan