public CellNumberFormatter()

in poi/src/main/java/org/apache/poi/ss/format/CellNumberFormatter.java [141:281]
118 lines of code
27 McCabe index (conditional complexity)

    public CellNumberFormatter(Locale locale, String format) {
        super(locale, format);

        CellNumberPartHandler ph = new CellNumberPartHandler();
        StringBuffer descBuf = CellFormatPart.parseFormat(format, CellFormatType.NUMBER, ph);

        exponent = ph.getExponent();
        specials.addAll(ph.getSpecials());
        improperFraction = ph.isImproperFraction();

        // These are inconsistent settings, so ditch 'em
        if ((ph.getDecimalPoint() != null || ph.getExponent() != null) && ph.getSlash() != null) {
            slash = null;
            numerator = null;
        } else {
            slash = ph.getSlash();
            numerator = ph.getNumerator();
        }

        final int precision = interpretPrecision(ph.getDecimalPoint(), specials);
        int fractionPartWidth = 0;
        if (ph.getDecimalPoint() != null) {
            fractionPartWidth = 1 + precision;
            if (precision == 0) {
                // This means the format has a ".", but that output should have no decimals after it.
                // We just stop treating it specially
                specials.remove(ph.getDecimalPoint());
                decimalPoint = null;
            } else {
                decimalPoint = ph.getDecimalPoint();
            }
        } else {
            decimalPoint = null;
        }

        if (decimalPoint != null) {
            afterInteger = decimalPoint;
        } else if (exponent != null) {
            afterInteger = exponent;
        } else if (numerator != null) {
            afterInteger = numerator;
        } else {
            afterInteger = null;
        }

        if (exponent != null) {
            afterFractional = exponent;
        } else if (numerator != null) {
            afterFractional = numerator;
        } else {
            afterFractional = null;
        }

        double[] scaleByRef = {ph.getScale()};
        showGroupingSeparator = interpretIntegerCommas(descBuf, specials, decimalPoint, integerEnd(), fractionalEnd(), scaleByRef);
        if (exponent == null) {
            scale = scaleByRef[0];
        } else {
            // in "e" formats,% and trailing commas have no scaling effect
            scale = 1;
        }

        if (precision != 0) {
            // TODO: if decimalPoint is null (-> index == -1), return the whole list?
            fractionalSpecials.addAll(specials.subList(specials.indexOf(decimalPoint) + 1, fractionalEnd()));
        }

        if (exponent != null) {
            int exponentPos = specials.indexOf(exponent);
            exponentSpecials.addAll(specialsFor(exponentPos, 2));
            exponentDigitSpecials.addAll(specialsFor(exponentPos + 2));
        }

        if (slash != null) {
            if (numerator != null) {
                numeratorSpecials.addAll(specialsFor(specials.indexOf(numerator)));
            }

            denominatorSpecials.addAll(specialsFor(specials.indexOf(slash) + 1));
            if (denominatorSpecials.isEmpty()) {
                // no denominator follows the slash, drop the fraction idea
                numeratorSpecials.clear();
                maxDenominator = 1;
                numeratorFmt = null;
                denominatorFmt = null;
            } else {
                maxDenominator = maxValue(denominatorSpecials);
                numeratorFmt = singleNumberFormat(numeratorSpecials);
                denominatorFmt = singleNumberFormat(denominatorSpecials);
            }
        } else {
            maxDenominator = 1;
            numeratorFmt = null;
            denominatorFmt = null;
        }

        integerSpecials.addAll(specials.subList(0, integerEnd()));

        if (exponent == null) {
            int integerPartWidth = calculateIntegerPartWidth();
            int totalWidth = integerPartWidth + fractionPartWidth;

            // need to handle empty width specially as %00.0f fails during formatting
            if(totalWidth == 0) {
                printfFmt = "";
            } else {
                printfFmt = "%0" + totalWidth + '.' + precision + "f";
            }
            decimalFmt = null;
        } else {
            StringBuffer fmtBuf = new StringBuffer();
            boolean first = true;
            if (integerSpecials.size() == 1) {
                // If we don't do this, we get ".6e5" instead of "6e4"
                fmtBuf.append("0");
                first = false;
            } else
                for (Special s : integerSpecials) {
                    if (isDigitFmt(s)) {
                        fmtBuf.append(first ? '#' : '0');
                        first = false;
                    }
                }
            if (!fractionalSpecials.isEmpty()) {
                fmtBuf.append('.');
                for (Special s : fractionalSpecials) {
                    if (isDigitFmt(s)) {
                        if (!first)
                            fmtBuf.append('0');
                        first = false;
                    }
                }
            }
            fmtBuf.append('E');
            placeZeros(fmtBuf, exponentSpecials.subList(2, exponentSpecials.size()));
            decimalFmt = new DecimalFormat(fmtBuf.toString(), getDecimalFormatSymbols());
            printfFmt = null;
        }

        desc = descBuf.toString();
    }