DecimalFormat is a concrete subclass of
NumberFormat that formats decimal numbers. It has a variety of
features designed to make it possible to parse and format numbers in any
locale, including support for Western, Arabic, and Indic digits. It also
supports different kinds of numbers, including integers (123), fixed-point
numbers (123.4), scientific notation (1.23E4), percentages (12%), and
currency amounts ($123). All of these can be localized.
To obtain a NumberFormat for a specific locale, including the
default locale, call one of NumberFormat's factory methods, such
as getInstance(). In general, do not call the
DecimalFormat constructors directly, since the
NumberFormat factory methods may return subclasses other than
DecimalFormat. If you need to customize the format object, do
something like this:
NumberFormat f = NumberFormat.getInstance(loc);
if (f instanceof DecimalFormat) {
((DecimalFormat) f).setDecimalSeparatorAlwaysShown(true);
}
A DecimalFormat comprises a pattern and a set of
symbols. The pattern may be set directly using
applyPattern(), or indirectly using the API methods. The
symbols are stored in a DecimalFormatSymbols object. When using
the NumberFormat factory methods, the pattern and symbols are
read from localized ResourceBundles.
DecimalFormat patterns have the following syntax:
Pattern:
PositivePattern
PositivePattern ; NegativePattern
PositivePattern:
Prefixopt Number Suffixopt
NegativePattern:
Prefixopt Number Suffixopt
Prefix:
any Unicode characters except \uFFFE, \uFFFF, and special characters
Suffix:
any Unicode characters except \uFFFE, \uFFFF, and special characters
Number:
Integer Exponentopt
Integer . Fraction Exponentopt
Integer:
MinimumInteger
#
# Integer
# , Integer
MinimumInteger:
0
0 MinimumInteger
0 , MinimumInteger
Fraction:
MinimumFractionopt OptionalFractionopt
MinimumFraction:
0 MinimumFractionopt
OptionalFraction:
# OptionalFractionopt
Exponent:
E MinimumExponent
MinimumExponent:
0 MinimumExponentopt
A DecimalFormat pattern contains a positive and negative
subpattern, for example, "#,##0.00;(#,##0.00)". Each
subpattern has a prefix, numeric part, and suffix. The negative subpattern
is optional; if absent, then the positive subpattern prefixed with the
localized minus sign ('-' in most locales) is used as the
negative subpattern. That is, "0.00" alone is equivalent to
"0.00;-0.00". If there is an explicit negative subpattern, it
serves only to specify the negative prefix and suffix; the number of digits,
minimal digits, and other characteristics are all the same as the positive
pattern. That means that "#,##0.0#;(#)" produces precisely
the same behavior as "#,##0.0#;(#,##0.0#)".
The prefixes, suffixes, and various symbols used for infinity, digits,
thousands separators, decimal separators, etc. may be set to arbitrary
values, and they will appear properly during formatting. However, care must
be taken that the symbols and strings do not conflict, or parsing will be
unreliable. For example, either the positive and negative prefixes or the
suffixes must be distinct for DecimalFormat.parse() to be able
to distinguish positive from negative values. (If they are identical, then
DecimalFormat will behave as if no negative subpattern was
specified.) Another example is that the decimal separator and thousands
separator should be distinct characters, or parsing will be impossible.
The grouping separator is commonly used for thousands, but in some
countries it separates ten-thousands. The grouping size is a constant number
of digits between the grouping characters, such as 3 for 100,000,000 or 4 for
1,0000,0000. If you supply a pattern with multiple grouping characters, the
interval between the last one and the end of the integer is the one that is
used. So "#,##,###,####" == "######,####" ==
"##,####,####".
Many characters in a pattern are taken literally; they are matched during parsing and output unchanged during formatting. Special characters, on the other hand, stand for other characters, strings, or classes of characters. They must be quoted, unless noted otherwise, if they are to appear in the prefix or suffix as literals.
The characters listed here are used in non-localized patterns. Localized
patterns use the corresponding characters taken from this formatter's
DecimalFormatSymbols object instead, and these characters lose
their special status. Two exceptions are the currency sign and quote, which
are not localized.
Symbol Location Localized? Meaning 0Number Yes Digit #Number Yes Digit, zero shows as absent .Number Yes Decimal separator or monetary decimal separator -Number Yes Minus sign ,Number Yes Grouping separator ENumber Yes Separates mantissa and exponent in scientific notation. Need not be quoted in prefix or suffix. ;Subpattern boundary Yes Separates positive and negative subpatterns %Prefix or suffix Yes Multiply by 100 and show as percentage \u2030Prefix or suffix Yes Multiply by 1000 and show as per mille value ¤(\u00A4)Prefix or suffix No Currency sign, replaced by currency symbol. If doubled, replaced by international currency symbol. If present in a pattern, the monetary decimal separator is used instead of the decimal separator. 'Prefix or suffix No Used to quote special characters in a prefix or suffix, for example, "'#'#"formats 123 to"#123". To create a single quote itself, use two in a row:"# o''clock".
Numbers in scientific notation are expressed as the product of a mantissa
and a power of ten, for example, 1234 can be expressed as 1.234 x 10^3. The
mantissa is often in the range 1.0 <= x < 10.0, but it need not be.
DecimalFormat can be instructed to format and parse scientific
notation only via a pattern; there is currently no factory method
that creates a scientific notation format. In a pattern, the exponent
character immediately followed by one or more digit characters indicates
scientific notation. Example: "0.###E0" formats the number
1234 as "1.234E3".
"0.###E0 m/s".
"##0.#####E0". Using this pattern, the number 12345
formats to "12.345E3", and 123456 formats to
"123.456E3".
"00.###E0" yields
"12.3E-4".
"##0.##E0" is "12.3E3". To show all digits, set
the significant digits count to zero. The number of significant digits
does not affect parsing.
DecimalFormat provides rounding modes defined in
java.math.RoundingModeRoundingMode.HALF_EVEN.
DecimalFormat uses the ten consecutive
characters starting with the localized zero digit defined in the
DecimalFormatSymbols object as digits. For parsing, these
digits as well as all Unicode decimal digits, as defined by
Character.digit, are recognized.
NaN is formatted as a string, which typically has a single character
\uFFFD. This string is determined by the
DecimalFormatSymbols object. This is the only value for which
the prefixes and suffixes are not used.
Infinity is formatted as a string, which typically has a single character
\u221E, with the positive or negative prefixes and suffixes
applied. The infinity string is determined by the
DecimalFormatSymbols object.
Negative zero ("-0") parses to
BigDecimal(0) if isParseBigDecimal() is
true,
Long(0) if isParseBigDecimal() is false
and isParseIntegerOnly() is true,
Double(-0.0) if both isParseBigDecimal()
and isParseIntegerOnly() are false.
Decimal 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.
// Print out a number using the localized number, integer, currency,
// and percent format for each locale
Locale[] locales = NumberFormat.getAvailableLocales();
double myNumber = -1234.56;
NumberFormat form;
for (int j=0; j<4; ++j) {
System.out.println("FORMAT");
for (int i = 0; i < locales.length; ++i) {
if (locales[i].getCountry().length() == 0) {
continue; // Skip language-only locales
}
System.out.print(locales[i].getDisplayName());
switch (j) {
case 0:
form = NumberFormat.getInstance(locales[i]); break;
case 1:
form = NumberFormat.getIntegerInstance(locales[i]); break;
case 2:
form = NumberFormat.getCurrencyInstance(locales[i]); break;
default:
form = NumberFormat.getPercentInstance(locales[i]); break;
}
if (form instanceof DecimalFormat) {
System.out.print(": " + ((DecimalFormat) form).toPattern());
}
System.out.print(" -> " + form.format(myNumber));
try {
System.out.println(" -> " + form.parse(form.format(myNumber)));
} catch (ParseException e) {}
}
}
NumberFormatDecimalFormatSymbolsParsePositionTo obtain standard formats for a given locale, use the factory methods on NumberFormat such as getNumberInstance. These factories will return the most appropriate sub-class of NumberFormat for a given locale.
To obtain standard formats for a given locale, use the factory methods on NumberFormat such as getNumberInstance. These factories will return the most appropriate sub-class of NumberFormat for a given locale.
pattern A non-localized pattern string.java.lang.NullPointerException if pattern is nulljava.lang.IllegalArgumentException if the given pattern is invalid.NumberFormat.getInstance()NumberFormat.getNumberInstance()NumberFormat.getCurrencyInstance()NumberFormat.getPercentInstance()To obtain standard formats for a given locale, use the factory methods on NumberFormat such as getInstance or getCurrencyInstance. If you need only minor adjustments to a standard format, you can modify the format returned by a NumberFormat factory method.
pattern a non-localized pattern stringsymbols the set of symbols to be usedjava.lang.NullPointerException if any of the given arguments is nulljava.lang.IllegalArgumentException if the given pattern is invalidNumberFormat.getInstance()NumberFormat.getNumberInstance()NumberFormat.getCurrencyInstance()NumberFormat.getPercentInstance()DecimalFormatSymbolsjava.lang.NumberThis implementation uses the maximum precision permitted.
number the number to formattoAppendTo the StringBuffer to which the formatted
text is to be appendedpos On input: an alignment field, if desired.
On output: the offsets of the alignment field.toAppendTojava.lang.IllegalArgumentException if number is
null or not an instance of Number.java.lang.NullPointerException if toAppendTo or
pos is nulljava.lang.ArithmeticException if rounding is needed with rounding
mode being set to RoundingMode.UNNECESSARYFieldPositionnumber The double to formatresult where the text is to be appendedfieldPosition On input: an alignment field, if desired.
On output: the offsets of the alignment field.java.lang.ArithmeticException if rounding is needed with rounding
mode being set to RoundingMode.UNNECESSARYFieldPositionnumber The double to formatresult where the text is to be appendeddelegate notified of locations of sub fieldsjava.lang.ArithmeticException if rounding is needed with rounding
mode being set to RoundingMode.UNNECESSARYnumber The long to formatresult where the text is to be appendedfieldPosition On input: an alignment field, if desired.
On output: the offsets of the alignment field.java.lang.ArithmeticException if rounding is needed with rounding
mode being set to RoundingMode.UNNECESSARYFieldPositionnumber The long to formatresult where the text is to be appendeddelegate notified of locations of sub fieldsjava.lang.ArithmeticException if rounding is needed with rounding
mode being set to RoundingMode.UNNECESSARYFieldPositionnumber The BigDecimal to formatresult where the text is to be appendedfieldPosition On input: an alignment field, if desired.
On output: the offsets of the alignment field.java.lang.ArithmeticException if rounding is needed with rounding
mode being set to RoundingMode.UNNECESSARYFieldPositionnumber The BigDecimal to formatresult where the text is to be appendeddelegate notified of locations of sub fieldsjava.lang.ArithmeticException if rounding is needed with rounding
mode being set to RoundingMode.UNNECESSARYnumber The BigInteger to formatresult where the text is to be appendedfieldPosition On input: an alignment field, if desired.
On output: the offsets of the alignment field.java.lang.ArithmeticException if rounding is needed with rounding
mode being set to RoundingMode.UNNECESSARYFieldPositionnumber The BigInteger to formatresult where the text is to be appendeddelegate notified of locations of sub fieldsjava.lang.ArithmeticException if rounding is needed with rounding
mode being set to RoundingMode.UNNECESSARYFieldPositionAttributedCharacterIterator.
You can use the returned AttributedCharacterIterator
to build the resulting String, as well as to determine information
about the resulting String.
Each attribute key of the AttributedCharacterIterator will be of type
NumberFormat.Field, with the attribute value being the
same as the attribute key.
obj The object to formatjava.lang.NullPointerException if obj is null.java.lang.IllegalArgumentException when the Format cannot format the
given object.java.lang.ArithmeticException if rounding is needed with rounding
mode being set to RoundingMode.UNNECESSARYstring to result.
delegate is notified of all the
FieldPositions in positions.
If one of the FieldPositions in positions
identifies a SIGN attribute, it is mapped to
signAttribute. This is used
to map the SIGN attribute to the EXPONENT
attribute as necessary.
This is used by subformat to add the prefix/suffix.
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.
The subclass returned depends on the value of isParseBigDecimal()
isParseBigDecimal() is false (the default),
most integer values are returned as Long
objects, no matter how they are written: "17" and
"17.000" both parse to Long(17).
Values that cannot fit into a Long are returned as
Doubles. This includes values with a fractional part,
infinite values, NaN, and the value -0.0.
DecimalFormat does not decide whether to
return a Double or a Long based on the
presence of a decimal separator in the source string. Doing so
would prevent integers that overflow the mantissa of a double,
such as "-9,223,372,036,854,775,808.00", from being
parsed accurately.
Callers may use the Number methods
doubleValue, longValue, etc., to obtain
the type they want.
isParseBigDecimal() is true, values are returned
as BigDecimal objects. The values are the ones
constructed by java.math.BigDecimal.(java.lang.String) Double instances holding the values of the
corresponding Double constants.
DecimalFormat parses all Unicode characters that represent
decimal digits, as defined by Character.digit(). In
addition, DecimalFormat also recognizes as digits the ten
consecutive characters starting with the localized zero digit defined in
the DecimalFormatSymbols object.
text the string to be parsedpos A ParsePosition object with index and error
index information as described above.null if the parse failsjava.lang.NullPointerException if text or
pos is null.text The string to parse.parsePosition The position at which to being parsing. Upon
return, the first unparseable character.digits The DigitList to set to the parsed value.isExponent If true, parse an exponent. This means no
infinite values and integer only.status Upon return contains boolean status flags indicating
whether the value was infinite and whether it was positive.if (subparse(text, pos, "", Character.toString(symbols.getMinusSign()), exponentDigits, true, stat) &&
DecimalFormatSymbolsnewSymbols desired DecimalFormatSymbolsDecimalFormatSymbolsExample: with multiplier 100, 1.23 is formatted as "123", and "123" is parsed into 1.23.
getMultiplier()parse(java.lang.String,java.text.ParsePosition)BigDecimal. The default value is false.
setParseBigDecimal(boolean)parse(java.lang.String,java.text.ParsePosition)BigDecimal.
isParseBigDecimal()applyPattern(java.lang.String)applyPattern(java.lang.String)pattern the non-null, possibly empty patternbuffer a scratch StringBuffer; its contents will be lostpattern the non-null, possibly empty patternbuffer the affix string is appended to thisaffixPattern a pattern such as posPrefixPattern; may be nullexpAffix a corresponding expanded affix, such as positivePrefix.
Ignored unless affixPattern is null. If affixPattern is null, then
expAffix is appended as a literal affix.localized true if the appended pattern should contain localized
pattern characters; otherwise, non-localized pattern chars are appendedThere is no limit to integer digits set by this routine, since that is the typical end-user desire; use setMaximumInteger if you want to set a real value. For negative numbers, use a second pattern, separated by a semicolon
Example "#,#00.0#" -> 1,234.56
This means a minimum of 2 integer digits, 1 fraction digit, and a maximum of 2 fraction digits.
Example: "#,#00.0#;(#,#00.0#)" for negatives in
parentheses.
In negative patterns, the minimum and maximum counts are ignored; these are presumed to be set in the positive pattern.
java.lang.NullPointerException if pattern is nulljava.lang.IllegalArgumentException if the given pattern is invalid.There is no limit to integer digits set by this routine, since that is the typical end-user desire; use setMaximumInteger if you want to set a real value. For negative numbers, use a second pattern, separated by a semicolon
Example "#,#00.0#" -> 1,234.56
This means a minimum of 2 integer digits, 1 fraction digit, and a maximum of 2 fraction digits.
Example: "#,#00.0#;(#,#00.0#)" for negatives in
parentheses.
In negative patterns, the minimum and maximum counts are ignored; these are presumed to be set in the positive pattern.
java.lang.NullPointerException if pattern is nulljava.lang.IllegalArgumentException if the given pattern is invalid.BigInteger and
BigDecimal objects, the lower of the return value and
309 is used.
setMaximumIntegerDigits(int)BigInteger and
BigDecimal objects, the lower of the return value and
309 is used.
setMinimumIntegerDigits(int)BigInteger and
BigDecimal objects, the lower of the return value and
340 is used.
setMaximumFractionDigits(int)BigInteger and
BigDecimal objects, the lower of the return value and
340 is used.
setMinimumFractionDigits(int)DecimalFormatSymbols.setCurrency
on this number format's symbols.
currency the new currency to be used by this decimal formatjava.lang.NullPointerException if currency is nulljava.math.RoundingModeRoundingMode used for this DecimalFormat.setRoundingMode(java.math.RoundingMode)java.math.RoundingModeroundingMode The RoundingMode to be usedjava.lang.NullPointerException if roundingMode is null.getRoundingMode()BigInteger and BigDecimal objects. These
limits are stored in the superclass for serialization compatibility
with older versions, while the limits for BigInteger and
BigDecimal objects are kept in this class.
If, in the superclass, the minimum or maximum integer digit count is
larger than DOUBLE_INTEGER_DIGITS or if the minimum or
maximum fraction digit count is larger than
DOUBLE_FRACTION_DIGITS, then the stream data is invalid
and this method throws an InvalidObjectException.
serialVersionOnStream is less than 4, initialize
roundingMode to RoundingMode.HALF_EVEN. This field is new with version 4.
serialVersionOnStream is less than 3, then call
the setters for the minimum and maximum integer and fraction digits with
the values of the corresponding superclass getters to initialize the
fields in this class. The fields in this class are new with version 3.
serialVersionOnStream is less than 1, indicating that
the stream was written by JDK 1.1, initialize
useExponentialNotation
to false, since it was not present in JDK 1.1.
serialVersionOnStream to the maximum allowed value so
that default serialization will work properly if this object is streamed
out again.
Stream versions older than 2 will not have the affix pattern variables
posPrefixPattern etc. As a result, they will be initialized
to null, which means the affix strings will be taken as
literal values. This is exactly what we want, since that corresponds to
the pre-version-2 behavior.
getPositivePrefix()getPositiveSuffix()getNegativePrefix()getNegativeSuffix()positivePrefix.
This pattern is expanded by the method expandAffix() to
positivePrefix to update the latter to reflect changes in
symbols. If this variable is null then
positivePrefix is taken as a literal value that does not
change when symbols changes. This variable is always
null for DecimalFormat objects older than
stream version 2 restored from stream.
NumberFormat.groupingUsed is true.
getGroupingSize()NumberFormat.isGroupingUsed()isDecimalSeparatorAlwaysShown()BigInteger or BigDecimal number.
maximumIntegerDigits must be greater than or equal to
minimumIntegerDigits.
getMaximumIntegerDigits()BigInteger or BigDecimal number.
minimumIntegerDigits must be less than or equal to
maximumIntegerDigits.
getMinimumIntegerDigits()BigInteger or BigDecimal number.
maximumFractionDigits must be greater than or equal to
minimumFractionDigits.
getMaximumFractionDigits()BigInteger or BigDecimal number.
minimumFractionDigits must be less than or equal to
maximumFractionDigits.
getMinimumFractionDigits()useExponentialNotation and
minExponentDigits.
posPrefixPattern, posSuffixPattern,
negPrefixPattern, and negSuffixPattern.
maximumIntegerDigits,
minimumIntegerDigits,
maximumFractionDigits,
minimumFractionDigits, and
parseBigDecimal.
roundingMode.