code: public DateTimeFormatterBuilder appendFraction(
              DateTimeFieldType fieldType, int minDigits, int maxDigits) {
          if (fieldType == null) {
              throw new IllegalArgumentException("Field type must not be null");
          }
          if (maxDigits < minDigits) {
              maxDigits = minDigits;
          }
          if (minDigits < 0 || maxDigits <= 0) {
              throw new IllegalArgumentException();
          }
          return append0(new Fraction(fieldType, minDigits, maxDigits));
      }
docs: Instructs the printer to emit a remainder of time as a decimal fraction,
  without decimal point. For example, if the field is specified as
  minuteOfHour and the time is 12:30:45, the value printed is 75. A
  decimal point is implied, so the fraction is 0.75, or three-quarters of
  a minute.
  
  @param fieldType  type of field to append
  @param minDigits  minimum number of digits to print.
  @param maxDigits  maximum number of digits to print or parse.
  @return this DateTimeFormatterBuilder, for chaining
  @throws IllegalArgumentException if field type is null