code: public static final Function<Number,String> toStr(Locale locale, int minIntegerDigits,
              int minFractionDigits, int maxFractionDigits, boolean groupingUsed) {
          return new ToString(NumberFormatType.NUMBER, locale, 
                  minIntegerDigits, Integer.MAX_VALUE, 
                  minFractionDigits, maxFractionDigits,
                  groupingUsed);
      }
docs: <p>
  It returns the {@link String} representation of the target number in the given {@link Locale}.
  If necessary, it will add leading or trailing zeros to the string based on the given parameters. So,
  </p>
  <code>toStr(Locale.ENGLISH, 3, 2, 2, true) would return 010.00 if target number is 10</code>
  <br />
  <code>toStr(Locale.ENGLISH, 2, 2, 4, true) would return 00.00 if target number is 0</code>
  
  @param locale the {@link Locale} to be used
  @param minIntegerDigits minimum number of integer digits so, if not enough in the
  target number, 0's will be added to the left of the integer part
  @param minFractionDigits minimum number of fraction digits so, if not enough in the
  target number, 0's will be added to the right of the decimal part
  @param maxFractionDigits
  @param groupingUsed whether or not grouping will be used
  @return the {@link String} representation of the input