code: void shutdownNow() {
      shutdown = true;
      for (int i = 0; i < channels.length; i++) {
        // Initiate channel shutdown
        channels[i].shutdown();
      }
      for (int i = 0; i < channels.length; i++) {
        try {
          // Wait for channel termination
          channels[i].awaitTermination(1, TimeUnit.SECONDS);
        } catch (InterruptedException ie) {
          channels[i].shutdownNow();
        }
      }
      fixedThreadPool.shutdownNow();
    }
docs: Shutdown the scenario as cleanly as possible.