code: public static final Function<Double,String> toStr(String locale, int minIntegerDigits, 
              int minFractionDigits, int maxFractionDigits, 
              char groupingSeparator, char decimalSeparator, boolean decimalSeparatorAlwaysShown) {
          return (Function<Double,String>)((Function)FnNumber.toStr(locale, 
                  minIntegerDigits, 
                  minFractionDigits, maxFractionDigits, 
                  groupingSeparator, decimalSeparator, 
                  decimalSeparatorAlwaysShown));
      }
docs: <p>
  It returns the {@link String} representation of the target number in the given locale.
  If necessary, it will add leading or trailing zeros to the string based on the given parameters. So,
  </p>
  <code>toStr(Locale.ENGLISH.toString(), 3, 2, 2, ',', '.', true) would return 1,000.00 if target number is 1000</code>
  <br />
  <code>toStr(Locale.ENGLISH.toString(), 2, 2, 4, ',', '.', true) would return 00.00 if target number is 0</code>
  
  @param locale the 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 maximum number of fraction digits
  @param groupingSeparator grouping separator to be used
  @param decimalSeparator decimal separator to be used
  @param decimalSeparatorAlwaysShown whether decimal separator should be shown
  even if the decimal part is zero or not
  @return the {@link String} representation of the input