code: private ChannelInfo getChannelInfo(int channelId) {
          ChannelInfo info = channels.putIfAbsent(channelId, new ChannelInfo());
          if (info == null) {
              info = channels.get(channelId);
          }
          return info;
      }
docs: Returns channel information for a given channel id.
  
  @param channelId
  @return channel info