code: public static NumberFormat format(int precision) {
          NumberFormat format = precisionFormat.get(precision);
          if (format == null) {
              precisionFormat.put(precision, createFormatter(precision));
          }
          return precisionFormat.get(precision);
      }
docs: Returns a number format that formats a number with the given
  number of precision digits. Parsing is not currently supported.
  
  @param precision number of digits past the decimal point
  @return a number format