code: public synchronized String[] getNotIncludedFiles() {
          slowScan();
          String[] files = new String[filesNotIncluded.size()];
          filesNotIncluded.copyInto(files);
          return files;
      }
docs: Return the names of the files which matched none of the include
  patterns. The names are relative to the base directory. This involves
  performing a slow scan if one has not already been completed.
  
  @return the names of the files which matched none of the include
  patterns.
  
  @see #slowScan