[jira] [Created] (LANG-1109) Number percentage formatting with fractional digits

[Marco Janc (JIRA)]

Marco Janc created LANG-1109:
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             Summary: Number percentage formatting with fractional digits
                 Key: LANG-1109
                 URL: https://issues.apache.org/jira/browse/LANG-1109
             Project: Commons Lang
          Issue Type: New Feature
          Components: lang.*
            Reporter: Marco Janc


Java built-in number formatter does formats Number locale aware with fractional 
digits defined by the defined scale of the Number, aswell the required 
precision (trims trailing zeros).

For some reason Java's built-in percentage number formatter does not formats 
fractional digits. So i wrote a function which has same behavior as the Java 
built-in number formatter but with percentage formatting.


        /**
         * Formats the given Number as percentage with necessary precision.
         * This serves as a workaround for {@link 
NumberFormat#getPercentInstance()} which does not renders fractional
         * digits.
         *
         * @param number
         * @param locale
         *
         * @return
         */
        public static String formatPercentFraction(final Number number, final 
Locale locale)
        {
                if (number == null)
                        return null;

                // get string representation with dot
                final String strNumber = 
NumberFormat.getNumberInstance(Locale.US).format(number.doubleValue());
                // create exact BigDecimal and convert to get scale
                final BigDecimal dNumber = new 
BigDecimal(strNumber).multiply(new BigDecimal(100));

                final NumberFormat percentScaleFormat = 
NumberFormat.getPercentInstance(locale);
                percentScaleFormat.setMaximumFractionDigits(Math.max(0, 
dNumber.scale()));

                // convert back for locale percent formatter
                return percentScaleFormat.format(dNumber.multiply(new 
BigDecimal(0.01)));
        }

I also unit tested it with many inputs.



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