code: public static void setCodecClasses(Configuration conf,
                                       List<Class> classes) {
      StringBuffer buf = new StringBuffer();
      Iterator<Class> itr = classes.iterator();
      if (itr.hasNext()) {
        Class cls = itr.next();
        buf.append(cls.getName());
        while(itr.hasNext()) {
          buf.append(',');
          buf.append(itr.next().getName());
        }
      }
      conf.set("io.compression.codecs", buf.toString());   
    }
docs: Sets a list of codec classes in the configuration.
  @param conf the configuration to modify
  @param classes the list of classes to set