code: private String format(double duration, Units units)
    {
      StringBuilder builder = new StringBuilder();
      builder.append(numberFormat.format(duration));
      builder.append(' ');
      builder.append(units.display());
      return builder.toString();
    }
docs: Build time duration representation for given numeric value and units.
  
  @param duration duration numeric part value,
  @param units bit rate units.
  @return formated bit rate.