code: public ConfigurationBuilder useParallelExecutor(final int availableProcessors) {
          ThreadFactory factory = new ThreadFactoryBuilder().setDaemon(true).setNameFormat("org.reflections-scanner-%d").build();
          setExecutorService(Executors.newFixedThreadPool(availableProcessors, factory));
          return this;
      }
docs: sets the executor service used for scanning to ThreadPoolExecutor with core size as the given availableProcessors parameter.
  the executor service spawns daemon threads by default.
  <p>default is ThreadPoolExecutor with a single core