code: public static EventLoopGroup newEventLoopGroup(int numThreads, String threadNamePrefix,
                                                     boolean useDaemonThreads) {
  
          checkArgument(numThreads > 0, "numThreads: %s (expected: > 0)", numThreads);
          requireNonNull(threadNamePrefix, "threadNamePrefix");
  
          final TransportType type = TransportType.detectTransportType();
          final String prefix = threadNamePrefix + '-' + type.lowerCasedName();
          return newEventLoopGroup(numThreads, new EventLoopThreadFactory(prefix, useDaemonThreads));
      }
docs: Returns a newly-created {@link EventLoopGroup}.
  
  @param numThreads the number of event loop threads
  @param threadNamePrefix the prefix of thread names
  @param useDaemonThreads whether to create daemon threads or not