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NumberFormat.javaAPI DocJava SE 5 API40536Fri Aug 26 14:57:20 BST 2005java.text

NumberFormat

public abstract class NumberFormat extends Format
NumberFormat is the abstract base class for all number formats. This class provides the interface for formatting and parsing numbers. NumberFormat also provides methods for determining which locales have number formats, and what their names are.

NumberFormat helps you to format and parse numbers for any locale. Your code can be completely independent of the locale conventions for decimal points, thousands-separators, or even the particular decimal digits used, or whether the number format is even decimal.

To format a number for the current Locale, use one of the factory class methods:

myString = NumberFormat.getInstance().format(myNumber);
If you are formatting multiple numbers, it is more efficient to get the format and use it multiple times so that the system doesn't have to fetch the information about the local language and country conventions multiple times.
NumberFormat nf = NumberFormat.getInstance();
for (int i = 0; i < a.length; ++i) {
output.println(nf.format(myNumber[i]) + "; ");
}
To format a number for a different Locale, specify it in the call to getInstance.
NumberFormat nf = NumberFormat.getInstance(Locale.FRENCH);
You can also use a NumberFormat to parse numbers:
myNumber = nf.parse(myString);
Use getInstance or getNumberInstance to get the normal number format. Use getIntegerInstance to get an integer number format. Use getCurrencyInstance to get the currency number format. And use getPercentInstance to get a format for displaying percentages. With this format, a fraction like 0.53 is displayed as 53%.

You can also control the display of numbers with such methods as setMinimumFractionDigits. If you want even more control over the format or parsing, or want to give your users more control, you can try casting the NumberFormat you get from the factory methods to a DecimalFormat. This will work for the vast majority of locales; just remember to put it in a try block in case you encounter an unusual one.

NumberFormat and DecimalFormat are designed such that some controls work for formatting and others work for parsing. The following is the detailed description for each these control methods,

setParseIntegerOnly : only affects parsing, e.g. if true, "3456.78" -> 3456 (and leaves the parse position just after index 6) if false, "3456.78" -> 3456.78 (and leaves the parse position just after index 8) This is independent of formatting. If you want to not show a decimal point where there might be no digits after the decimal point, use setDecimalSeparatorAlwaysShown.

setDecimalSeparatorAlwaysShown : only affects formatting, and only where there might be no digits after the decimal point, such as with a pattern like "#,##0.##", e.g., if true, 3456.00 -> "3,456." if false, 3456.00 -> "3456" This is independent of parsing. If you want parsing to stop at the decimal point, use setParseIntegerOnly.

You can also use forms of the parse and format methods with ParsePosition and FieldPosition to allow you to:

  • progressively parse through pieces of a string
  • align the decimal point and other areas
For example, you can align numbers in two ways:
  1. If you are using a monospaced font with spacing for alignment, you can pass the FieldPosition in your format call, with field = INTEGER_FIELD. On output, getEndIndex will be set to the offset between the last character of the integer and the decimal. Add (desiredSpaceCount - getEndIndex) spaces at the front of the string.
  2. If you are using proportional fonts, instead of padding with spaces, measure the width of the string in pixels from the start to getEndIndex. Then move the pen by (desiredPixelWidth - widthToAlignmentPoint) before drawing the text. It also works where there is no decimal, but possibly additional characters at the end, e.g., with parentheses in negative numbers: "(12)" for -12.

Synchronization

Number formats are generally not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally.

see
DecimalFormat
see
ChoiceFormat
version
1.65, 05/10/04
author
Mark Davis
author
Helena Shih

Fields Summary
public static final int
INTEGER_FIELD
Field constant used to construct a FieldPosition object. Signifies that the position of the integer part of a formatted number should be returned.
public static final int
FRACTION_FIELD
Field constant used to construct a FieldPosition object. Signifies that the position of the fraction part of a formatted number should be returned.
private static final Hashtable
cachedLocaleData
Cache to hold the NumberPatterns of a Locale.
private static final int
NUMBERSTYLE
private static final int
CURRENCYSTYLE
private static final int
PERCENTSTYLE
private static final int
SCIENTIFICSTYLE
private static final int
INTEGERSTYLE
private boolean
groupingUsed
True if the the grouping (i.e. thousands) separator is used when formatting and parsing numbers.
private byte
maxIntegerDigits
The maximum number of digits allowed in the integer portion of a number. maxIntegerDigits must be greater than or equal to minIntegerDigits.

Note: This field exists only for serialization compatibility with JDK 1.1. In Java platform 2 v1.2 and higher, the new int field maximumIntegerDigits is used instead. When writing to a stream, maxIntegerDigits is set to maximumIntegerDigits or Byte.MAX_VALUE, whichever is smaller. When reading from a stream, this field is used only if serialVersionOnStream is less than 1.

private byte
minIntegerDigits
The minimum number of digits allowed in the integer portion of a number. minimumIntegerDigits must be less than or equal to maximumIntegerDigits.

Note: This field exists only for serialization compatibility with JDK 1.1. In Java platform 2 v1.2 and higher, the new int field minimumIntegerDigits is used instead. When writing to a stream, minIntegerDigits is set to minimumIntegerDigits or Byte.MAX_VALUE, whichever is smaller. When reading from a stream, this field is used only if serialVersionOnStream is less than 1.

private byte
maxFractionDigits
The maximum number of digits allowed in the fractional portion of a number. maximumFractionDigits must be greater than or equal to minimumFractionDigits.

Note: This field exists only for serialization compatibility with JDK 1.1. In Java platform 2 v1.2 and higher, the new int field maximumFractionDigits is used instead. When writing to a stream, maxFractionDigits is set to maximumFractionDigits or Byte.MAX_VALUE, whichever is smaller. When reading from a stream, this field is used only if serialVersionOnStream is less than 1.

private byte
minFractionDigits
The minimum number of digits allowed in the fractional portion of a number. minimumFractionDigits must be less than or equal to maximumFractionDigits.

Note: This field exists only for serialization compatibility with JDK 1.1. In Java platform 2 v1.2 and higher, the new int field minimumFractionDigits is used instead. When writing to a stream, minFractionDigits is set to minimumFractionDigits or Byte.MAX_VALUE, whichever is smaller. When reading from a stream, this field is used only if serialVersionOnStream is less than 1.

private boolean
parseIntegerOnly
True if this format will parse numbers as integers only.
private int
maximumIntegerDigits
The maximum number of digits allowed in the integer portion of a number. maximumIntegerDigits must be greater than or equal to minimumIntegerDigits.
private int
minimumIntegerDigits
The minimum number of digits allowed in the integer portion of a number. minimumIntegerDigits must be less than or equal to maximumIntegerDigits.
private int
maximumFractionDigits
The maximum number of digits allowed in the fractional portion of a number. maximumFractionDigits must be greater than or equal to minimumFractionDigits.
private int
minimumFractionDigits
The minimum number of digits allowed in the fractional portion of a number. minimumFractionDigits must be less than or equal to maximumFractionDigits.
static final int
currentSerialVersion
private int
serialVersionOnStream
Describes the version of NumberFormat present on the stream. Possible values are:
  • 0 (or uninitialized): the JDK 1.1 version of the stream format. In this version, the int fields such as maximumIntegerDigits were not present, and the byte fields such as maxIntegerDigits are used instead.
  • 1: the 1.2 version of the stream format. The values of the byte fields such as maxIntegerDigits are ignored, and the int fields such as maximumIntegerDigits are used instead.
When streaming out a NumberFormat, the most recent format (corresponding to the highest allowable serialVersionOnStream) is always written.
static final long
serialVersionUID
Constructors Summary
Methods Summary
public java.lang.Objectclone()
Overrides Cloneable

        NumberFormat other = (NumberFormat) super.clone();
        return other;
    
public booleanequals(java.lang.Object obj)
Overrides equals

        if (obj == null) {
            return false;
        }
        if (this == obj) {
            return true;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        NumberFormat other = (NumberFormat) obj;
        return (maximumIntegerDigits == other.maximumIntegerDigits
            && minimumIntegerDigits == other.minimumIntegerDigits
            && maximumFractionDigits == other.maximumFractionDigits
            && minimumFractionDigits == other.minimumFractionDigits
            && groupingUsed == other.groupingUsed
            && parseIntegerOnly == other.parseIntegerOnly);
    
public java.lang.StringBufferformat(java.lang.Object number, java.lang.StringBuffer toAppendTo, java.text.FieldPosition pos)
Formats a number and appends the resulting text to the given string buffer. The number can be of any subclass of {@link java.lang.Number}.

This implementation extracts the number's value using {@link java.lang.Number#longValue()} for all integral type values that can be converted to long without loss of information, including BigInteger values with a {@link java.math.BigInteger#bitLength() bit length} of less than 64, and {@link java.lang.Number#doubleValue()} for all other types. It then calls {@link #format(long,java.lang.StringBuffer,java.text.FieldPosition)} or {@link #format(double,java.lang.StringBuffer,java.text.FieldPosition)}. This may result in loss of magnitude information and precision for BigInteger and BigDecimal values.

param
number the number to format
param
toAppendTo the StringBuffer to which the formatted text is to be appended
param
pos On input: an alignment field, if desired. On output: the offsets of the alignment field.
return
the value passed in as toAppendTo
exception
IllegalArgumentException if number is null or not an instance of Number.
exception
NullPointerException if toAppendTo or pos is null
see
java.text.FieldPosition


                                                                                                                                                                                                                                                                                             
       
                                
                                 
        if (number instanceof Long || number instanceof Integer ||
            number instanceof Short || number instanceof Byte ||
            (number instanceof BigInteger &&
             ((BigInteger)number).bitLength() < 64)) {
            return format(((Number)number).longValue(), toAppendTo, pos);
        } else if (number instanceof Number) {
            return format(((Number)number).doubleValue(), toAppendTo, pos);
        } else {
            throw new IllegalArgumentException("Cannot format given Object as a Number");
        }
    
public final java.lang.Stringformat(double number)
Specialization of format.

see
java.text.Format#format

        return format(number, new StringBuffer(),
                      DontCareFieldPosition.INSTANCE).toString();
    
public final java.lang.Stringformat(long number)
Specialization of format.

see
java.text.Format#format

        return format(number, new StringBuffer(),
                      DontCareFieldPosition.INSTANCE).toString();
    
public abstract java.lang.StringBufferformat(double number, java.lang.StringBuffer toAppendTo, java.text.FieldPosition pos)
Specialization of format.

see
java.text.Format#format

public abstract java.lang.StringBufferformat(long number, java.lang.StringBuffer toAppendTo, java.text.FieldPosition pos)
Specialization of format.

see
java.text.Format#format

public static java.util.Locale[]getAvailableLocales()
Returns an array of all locales for which the get*Instance methods of this class can return localized instances. The array returned must contain at least a Locale instance equal to {@link java.util.Locale#US Locale.US}.

return
An array of locales for which localized NumberFormat instances are available.

        return LocaleData.getAvailableLocales("NumberPatterns");
    
public java.util.CurrencygetCurrency()
Gets the currency used by this number format when formatting currency values. The initial value is derived in a locale dependent way. The returned value may be null if no valid currency could be determined and no currency has been set using {@link #setCurrency(java.util.Currency) setCurrency}.

The default implementation throws UnsupportedOperationException.

return
the currency used by this number format, or null
exception
UnsupportedOperationException if the number format class doesn't implement currency formatting
since
1.4

        throw new UnsupportedOperationException();
    
public static final java.text.NumberFormatgetCurrencyInstance()
Returns a currency format for the current default locale.

        return getInstance(Locale.getDefault(), CURRENCYSTYLE);
    
public static java.text.NumberFormatgetCurrencyInstance(java.util.Locale inLocale)
Returns a currency format for the specified locale.

        return getInstance(inLocale, CURRENCYSTYLE);
    
public static final java.text.NumberFormatgetInstance()
Returns a general-purpose number format for the current default locale. This is the same as calling {@link #getNumberInstance() getNumberInstance()}.

        return getInstance(Locale.getDefault(), NUMBERSTYLE);
    
public static java.text.NumberFormatgetInstance(java.util.Locale inLocale)
Returns a general-purpose number format for the specified locale. This is the same as calling {@link #getNumberInstance(java.util.Locale) getNumberInstance(inLocale)}.

        return getInstance(inLocale, NUMBERSTYLE);
    
private static java.text.NumberFormatgetInstance(java.util.Locale desiredLocale, int choice)

        /* try the cache first */
        String[] numberPatterns = (String[])cachedLocaleData.get(desiredLocale);
        if (numberPatterns == null) { /* cache miss */
            ResourceBundle resource = LocaleData.getLocaleElements(desiredLocale);
            numberPatterns = resource.getStringArray("NumberPatterns");
            /* update cache */
            cachedLocaleData.put(desiredLocale, numberPatterns);
        }
        
        DecimalFormatSymbols symbols = new DecimalFormatSymbols(desiredLocale);
        int entry = (choice == INTEGERSTYLE) ? NUMBERSTYLE : choice;
        DecimalFormat format = new DecimalFormat(numberPatterns[entry], symbols);
        
        if (choice == INTEGERSTYLE) {
            format.setMaximumFractionDigits(0);
            format.setDecimalSeparatorAlwaysShown(false);
            format.setParseIntegerOnly(true);
        } else if (choice == CURRENCYSTYLE) {
            format.adjustForCurrencyDefaultFractionDigits();
        }

        return format;
    
public static final java.text.NumberFormatgetIntegerInstance()
Returns an integer number format for the current default locale. The returned number format is configured to round floating point numbers to the nearest integer using IEEE half-even rounding (see {@link java.math.BigDecimal#ROUND_HALF_EVEN ROUND_HALF_EVEN}) for formatting, and to parse only the integer part of an input string (see {@link #isParseIntegerOnly isParseIntegerOnly}).

return
a number format for integer values
since
1.4

        return getInstance(Locale.getDefault(), INTEGERSTYLE);
    
public static java.text.NumberFormatgetIntegerInstance(java.util.Locale inLocale)
Returns an integer number format for the specified locale. The returned number format is configured to round floating point numbers to the nearest integer using IEEE half-even rounding (see {@link java.math.BigDecimal#ROUND_HALF_EVEN ROUND_HALF_EVEN}) for formatting, and to parse only the integer part of an input string (see {@link #isParseIntegerOnly isParseIntegerOnly}).

param
inLocale the locale for which a number format is needed
return
a number format for integer values
since
1.4

        return getInstance(inLocale, INTEGERSTYLE);
    
public intgetMaximumFractionDigits()
Returns the maximum number of digits allowed in the fraction portion of a number.

see
#setMaximumFractionDigits

        return maximumFractionDigits;
    
public intgetMaximumIntegerDigits()
Returns the maximum number of digits allowed in the integer portion of a number.

see
#setMaximumIntegerDigits

        return maximumIntegerDigits;
    
public intgetMinimumFractionDigits()
Returns the minimum number of digits allowed in the fraction portion of a number.

see
#setMinimumFractionDigits

        return minimumFractionDigits;
    
public intgetMinimumIntegerDigits()
Returns the minimum number of digits allowed in the integer portion of a number.

see
#setMinimumIntegerDigits

        return minimumIntegerDigits;
    
public static final java.text.NumberFormatgetNumberInstance()
Returns a general-purpose number format for the current default locale.

        return getInstance(Locale.getDefault(), NUMBERSTYLE);
    
public static java.text.NumberFormatgetNumberInstance(java.util.Locale inLocale)
Returns a general-purpose number format for the specified locale.

        return getInstance(inLocale, NUMBERSTYLE);
    
public static final java.text.NumberFormatgetPercentInstance()
Returns a percentage format for the current default locale.

        return getInstance(Locale.getDefault(), PERCENTSTYLE);
    
public static java.text.NumberFormatgetPercentInstance(java.util.Locale inLocale)
Returns a percentage format for the specified locale.

        return getInstance(inLocale, PERCENTSTYLE);
    
static final java.text.NumberFormatgetScientificInstance()
Returns a scientific format for the current default locale.

        return getInstance(Locale.getDefault(), SCIENTIFICSTYLE);
    
static java.text.NumberFormatgetScientificInstance(java.util.Locale inLocale)
Returns a scientific format for the specified locale.

        return getInstance(inLocale, SCIENTIFICSTYLE);
    
public inthashCode()
Overrides hashCode

        return maximumIntegerDigits * 37 + maxFractionDigits;
        // just enough fields for a reasonable distribution
    
public booleanisGroupingUsed()
Returns true if grouping is used in this format. For example, in the English locale, with grouping on, the number 1234567 might be formatted as "1,234,567". The grouping separator as well as the size of each group is locale dependant and is determined by sub-classes of NumberFormat.

see
#setGroupingUsed

        return groupingUsed;
    
public booleanisParseIntegerOnly()
Returns true if this format will parse numbers as integers only. For example in the English locale, with ParseIntegerOnly true, the string "1234." would be parsed as the integer value 1234 and parsing would stop at the "." character. Of course, the exact format accepted by the parse operation is locale dependant and determined by sub-classes of NumberFormat.

        return parseIntegerOnly;
    
public abstract java.lang.Numberparse(java.lang.String source, java.text.ParsePosition parsePosition)
Returns a Long if possible (e.g., within the range [Long.MIN_VALUE, Long.MAX_VALUE] and with no decimals), otherwise a Double. If IntegerOnly is set, will stop at a decimal point (or equivalent; e.g., for rational numbers "1 2/3", will stop after the 1). Does not throw an exception; if no object can be parsed, index is unchanged!

see
java.text.NumberFormat#isParseIntegerOnly
see
java.text.Format#parseObject

public java.lang.Numberparse(java.lang.String source)
Parses text from the beginning of the given string to produce a number. The method may not use the entire text of the given string.

See the {@link #parse(String, ParsePosition)} method for more information on number parsing.

param
source A String whose beginning should be parsed.
return
A Number parsed from the string.
exception
ParseException if the beginning of the specified string cannot be parsed.

        ParsePosition parsePosition = new ParsePosition(0);
        Number result = parse(source, parsePosition);
        if (parsePosition.index == 0) {
            throw new ParseException("Unparseable number: \"" + source + "\"",
                                     parsePosition.errorIndex);
        }
        return result;
    
public final java.lang.ObjectparseObject(java.lang.String source, java.text.ParsePosition pos)
Parses text from a string to produce a Number.

The method attempts to parse text starting at the index given by pos. If parsing succeeds, then the index of pos is updated to the index after the last character used (parsing does not necessarily use all characters up to the end of the string), and the parsed number is returned. The updated pos can be used to indicate the starting point for the next call to this method. If an error occurs, then the index of pos is not changed, the error index of pos is set to the index of the character where the error occurred, and null is returned.

See the {@link #parse(String, ParsePosition)} method for more information on number parsing.

param
source A String, part of which should be parsed.
param
pos A ParsePosition object with index and error index information as described above.
return
A Number parsed from the string. In case of error, returns null.
exception
NullPointerException if pos is null.

        return parse(source, pos);
    
private voidreadObject(java.io.ObjectInputStream stream)
First, read in the default serializable data. Then, if serialVersionOnStream is less than 1, indicating that the stream was written by JDK 1.1, set the int fields such as maximumIntegerDigits to be equal to the byte fields such as maxIntegerDigits, since the int fields were not present in JDK 1.1. Finally, set serialVersionOnStream back to the maximum allowed value so that default serialization will work properly if this object is streamed out again.

If minimumIntegerDigits is greater than maximumIntegerDigits or minimumFractionDigits is greater than maximumFractionDigits, then the stream data is invalid and this method throws an InvalidObjectException. In addition, if any of these values is negative, then this method throws an InvalidObjectException.

since
1.2

        stream.defaultReadObject();
        if (serialVersionOnStream < 1) {
            // Didn't have additional int fields, reassign to use them.
            maximumIntegerDigits = maxIntegerDigits;
            minimumIntegerDigits = minIntegerDigits;
            maximumFractionDigits = maxFractionDigits;
            minimumFractionDigits = minFractionDigits;
        }
        if (minimumIntegerDigits > maximumIntegerDigits ||
            minimumFractionDigits > maximumFractionDigits ||
            minimumIntegerDigits < 0 || minimumFractionDigits < 0) {
            throw new InvalidObjectException("Digit count range invalid");
        }
        serialVersionOnStream = currentSerialVersion;
    
public voidsetCurrency(java.util.Currency currency)
Sets the currency used by this number format when formatting currency values. This does not update the minimum or maximum number of fraction digits used by the number format.

The default implementation throws UnsupportedOperationException.

param
currency the new currency to be used by this number format
exception
UnsupportedOperationException if the number format class doesn't implement currency formatting
exception
NullPointerException if currency is null
since
1.4

        throw new UnsupportedOperationException();
    
public voidsetGroupingUsed(boolean newValue)
Set whether or not grouping will be used in this format.

see
#isGroupingUsed

        groupingUsed = newValue;
    
public voidsetMaximumFractionDigits(int newValue)
Sets the maximum number of digits allowed in the fraction portion of a number. maximumFractionDigits must be >= minimumFractionDigits. If the new value for maximumFractionDigits is less than the current value of minimumFractionDigits, then minimumFractionDigits will also be set to the new value.

param
newValue the maximum number of fraction digits to be shown; if less than zero, then zero is used. The concrete subclass may enforce an upper limit to this value appropriate to the numeric type being formatted.
see
#getMaximumFractionDigits

        maximumFractionDigits = Math.max(0,newValue);
        if (maximumFractionDigits < minimumFractionDigits) {
            minimumFractionDigits = maximumFractionDigits;
        }
    
public voidsetMaximumIntegerDigits(int newValue)
Sets the maximum number of digits allowed in the integer portion of a number. maximumIntegerDigits must be >= minimumIntegerDigits. If the new value for maximumIntegerDigits is less than the current value of minimumIntegerDigits, then minimumIntegerDigits will also be set to the new value.

param
newValue the maximum number of integer digits to be shown; if less than zero, then zero is used. The concrete subclass may enforce an upper limit to this value appropriate to the numeric type being formatted.
see
#getMaximumIntegerDigits

        maximumIntegerDigits = Math.max(0,newValue);
        if (minimumIntegerDigits > maximumIntegerDigits) {
            minimumIntegerDigits = maximumIntegerDigits;
        }
    
public voidsetMinimumFractionDigits(int newValue)
Sets the minimum number of digits allowed in the fraction portion of a number. minimumFractionDigits must be <= maximumFractionDigits. If the new value for minimumFractionDigits exceeds the current value of maximumFractionDigits, then maximumIntegerDigits will also be set to the new value

param
newValue the minimum number of fraction digits to be shown; if less than zero, then zero is used. The concrete subclass may enforce an upper limit to this value appropriate to the numeric type being formatted.
see
#getMinimumFractionDigits

        minimumFractionDigits = Math.max(0,newValue);
        if (maximumFractionDigits < minimumFractionDigits) {
            maximumFractionDigits = minimumFractionDigits;
        }
    
public voidsetMinimumIntegerDigits(int newValue)
Sets the minimum number of digits allowed in the integer portion of a number. minimumIntegerDigits must be <= maximumIntegerDigits. If the new value for minimumIntegerDigits exceeds the current value of maximumIntegerDigits, then maximumIntegerDigits will also be set to the new value

param
newValue the minimum number of integer digits to be shown; if less than zero, then zero is used. The concrete subclass may enforce an upper limit to this value appropriate to the numeric type being formatted.
see
#getMinimumIntegerDigits

        minimumIntegerDigits = Math.max(0,newValue);
        if (minimumIntegerDigits > maximumIntegerDigits) {
            maximumIntegerDigits = minimumIntegerDigits;
        }
    
public voidsetParseIntegerOnly(boolean value)
Sets whether or not numbers should be parsed as integers only.

see
#isParseIntegerOnly

        parseIntegerOnly = value;
    
private voidwriteObject(java.io.ObjectOutputStream stream)
Write out the default serializable data, after first setting the byte fields such as maxIntegerDigits to be equal to the int fields such as maximumIntegerDigits (or to Byte.MAX_VALUE, whichever is smaller), for compatibility with the JDK 1.1 version of the stream format.

since
1.2

        maxIntegerDigits = (maximumIntegerDigits > Byte.MAX_VALUE) ?
                           Byte.MAX_VALUE : (byte)maximumIntegerDigits;
        minIntegerDigits = (minimumIntegerDigits > Byte.MAX_VALUE) ?
                           Byte.MAX_VALUE : (byte)minimumIntegerDigits;
        maxFractionDigits = (maximumFractionDigits > Byte.MAX_VALUE) ?
                            Byte.MAX_VALUE : (byte)maximumFractionDigits;
        minFractionDigits = (minimumFractionDigits > Byte.MAX_VALUE) ?
                            Byte.MAX_VALUE : (byte)minimumFractionDigits;
        stream.defaultWriteObject();