- All Implemented Interfaces:
Serializable
,Cloneable
- Direct Known Subclasses:
ChoiceFormat
,CompactNumberFormat
,DecimalFormat
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:
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.myString = NumberFormat.getInstance().format(myNumber);
To format a number for a different Locale, specify it in the call toNumberFormat nf = NumberFormat.getInstance(); for (var myNumber : numbers) { output.println(nf.format(myNumber) + "; "); }
getInstance
.
NumberFormat nf = NumberFormat.getInstance(Locale.FRENCH);
If the locale contains "nu" (numbers) and/or "rg" (region override) Unicode extensions, the decimal digits, and/or the country used for formatting are overridden. If both "nu" and "rg" are specified, the decimal digits from the "nu" extension supersedes the implicit one from the "rg" extension.
You can also use a NumberFormat
to parse numbers:
UsemyNumber = nf.parse(myString);
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. Use getCompactNumberInstance
to get the
compact number format to format a number in shorter form. For example,
2000
can be formatted as "2K"
in
US locale
. 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
or CompactNumberFormat
depending on
the factory method used. 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
- If you are using a monospaced font with spacing for alignment,
you can pass the
FieldPosition
in your format call, withfield
=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. - 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.
- Implementation Requirements:
- The
format(double, StringBuffer, FieldPosition)
,format(long, StringBuffer, FieldPosition)
andparse(String, ParsePosition)
methods may throwNullPointerException
, if any of their parameter isnull
. The subclass may provide its own implementation and specification aboutNullPointerException
.The default implementation provides rounding modes defined in
RoundingMode
for formatting numbers. It uses the round half-even algorithm. To change the rounding mode usesetRoundingMode
. TheNumberFormat
returned by the static factory methods is configured to round floating point numbers using half-even rounding (seeRoundingMode.HALF_EVEN
) for formatting. - Since:
- 1.1
- See Also:
-
Nested Class Summary
Modifier and TypeClassDescriptionstatic class
Defines constants that are used as attribute keys in theAttributedCharacterIterator
returned fromNumberFormat.formatToCharacterIterator
and as field identifiers inFieldPosition
.static enum
A number format style. -
Field Summary
Modifier and TypeFieldDescriptionstatic final int
Field constant used to construct a FieldPosition object.static final int
Field constant used to construct a FieldPosition object. -
Constructor Summary
-
Method Summary
Modifier and TypeMethodDescriptionclone()
Overrides Cloneable.boolean
Compares the specified object with thisNumberFormat
for equality.final String
format
(double number) Specialization of format.abstract StringBuffer
format
(double number, StringBuffer toAppendTo, FieldPosition pos) Specialization of format.final String
format
(long number) Specialization of format.abstract StringBuffer
format
(long number, StringBuffer toAppendTo, FieldPosition pos) Specialization of format.format
(Object number, StringBuffer toAppendTo, FieldPosition pos) Formats a number and appends the resulting text to the given string buffer.static Locale[]
Returns an array of all locales for which theget*Instance
methods of this class can return localized instances.static NumberFormat
static NumberFormat
getCompactNumberInstance
(Locale locale, NumberFormat.Style formatStyle) Returns a compact number format for the specifiedlocale
andformatStyle
.Gets the currency used by this number format when formatting currency values.static final NumberFormat
Returns a currency format for the current defaultFORMAT
locale.static NumberFormat
getCurrencyInstance
(Locale inLocale) Returns a currency format for the specified locale.static final NumberFormat
Returns a general-purpose number format for the current defaultFORMAT
locale.static NumberFormat
getInstance
(Locale inLocale) Returns a general-purpose number format for the specified locale.static final NumberFormat
Returns an integer number format for the current defaultFORMAT
locale.static NumberFormat
getIntegerInstance
(Locale inLocale) Returns an integer number format for the specified locale.int
Returns the maximum number of digits allowed in the fraction portion of a number.int
Returns the maximum number of digits allowed in the integer portion of a number.int
Returns the minimum number of digits allowed in the fraction portion of a number.int
Returns the minimum number of digits allowed in the integer portion of a number.static final NumberFormat
Returns a general-purpose number format for the current defaultFORMAT
locale.static NumberFormat
getNumberInstance
(Locale inLocale) Returns a general-purpose number format for the specified locale.static final NumberFormat
Returns a percentage format for the current defaultFORMAT
locale.static NumberFormat
getPercentInstance
(Locale inLocale) Returns a percentage format for the specified locale.Gets theRoundingMode
used in this NumberFormat.int
hashCode()
Returns the hash code for thisNumberFormat
.boolean
Returns true if grouping is used in this format.boolean
Returns true if this format will parse numbers as integers only.Parses text from the beginning of the given string to produce a number.abstract Number
parse
(String source, 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.final Object
parseObject
(String source, ParsePosition pos) Parses text from a string to produce aNumber
.void
setCurrency
(Currency currency) Sets the currency used by this number format when formatting currency values.void
setGroupingUsed
(boolean newValue) Set whether or not grouping will be used in this format.void
setMaximumFractionDigits
(int newValue) Sets the maximum number of digits allowed in the fraction portion of a number. maximumFractionDigits must be ≥ minimumFractionDigits.void
setMaximumIntegerDigits
(int newValue) Sets the maximum number of digits allowed in the integer portion of a number. maximumIntegerDigits must be ≥ minimumIntegerDigits.void
setMinimumFractionDigits
(int newValue) Sets the minimum number of digits allowed in the fraction portion of a number. minimumFractionDigits must be ≤ maximumFractionDigits.void
setMinimumIntegerDigits
(int newValue) Sets the minimum number of digits allowed in the integer portion of a number. minimumIntegerDigits must be ≤ maximumIntegerDigits.void
setParseIntegerOnly
(boolean value) Sets whether or not numbers should be parsed as integers only.void
setRoundingMode
(RoundingMode roundingMode) Sets theRoundingMode
used in this NumberFormat.Methods declared in class java.text.Format
format, formatToCharacterIterator, parseObject
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Field Details
-
INTEGER_FIELD
public static final int INTEGER_FIELDField constant used to construct a FieldPosition object. Signifies that the position of the integer part of a formatted number should be returned.- See Also:
-
FRACTION_FIELD
public static final int FRACTION_FIELDField constant used to construct a FieldPosition object. Signifies that the position of the fraction part of a formatted number should be returned.- See Also:
-
-
Constructor Details
-
NumberFormat
protected NumberFormat()Sole constructor. (For invocation by subclass constructors, typically implicit.)
-
-
Method Details
-
format
Formats a number and appends the resulting text to the given string buffer. The number can be of any subclass ofNumber
.This implementation extracts the number's value using
Number.longValue()
for all integral type values that can be converted tolong
without loss of information, includingBigInteger
values with abit length
of less than 64, andNumber.doubleValue()
for all other types. It then callsformat(long,java.lang.StringBuffer,java.text.FieldPosition)
orformat(double,java.lang.StringBuffer,java.text.FieldPosition)
. This may result in loss of magnitude information and precision forBigInteger
andBigDecimal
values.- Specified by:
format
in classFormat
- Parameters:
number
- the number to formattoAppendTo
- theStringBuffer
to which the formatted text is to be appendedpos
- keeps track on the position of the field within the returned string. For example, for formatting a number1234567.89
inLocale.US
locale, if the givenfieldPosition
isINTEGER_FIELD
, the begin index and end index offieldPosition
will be set to 0 and 9, respectively for the output string1,234,567.89
.- Returns:
- the value passed in as
toAppendTo
- Throws:
IllegalArgumentException
- ifnumber
is null or not an instance ofNumber
.NullPointerException
- iftoAppendTo
orpos
is nullArithmeticException
- if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY- See Also:
-
parseObject
Parses text from a string to produce aNumber
.The method attempts to parse text starting at the index given by
pos
. If parsing succeeds, then the index ofpos
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 updatedpos
can be used to indicate the starting point for the next call to this method. If an error occurs, then the index ofpos
is not changed, the error index ofpos
is set to the index of the character where the error occurred, and null is returned.See the
parse(String, ParsePosition)
method for more information on number parsing.- Specified by:
parseObject
in classFormat
- Parameters:
source
- AString
, part of which should be parsed.pos
- AParsePosition
object with index and error index information as described above.- Returns:
- A
Number
parsed from the string. In case of error, returns null. - Throws:
NullPointerException
- ifsource
orpos
is null.
-
format
Specialization of format.- Parameters:
number
- the double number to format- Returns:
- the formatted String
- Throws:
ArithmeticException
- if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY- See Also:
-
format
Specialization of format.- Parameters:
number
- the long number to format- Returns:
- the formatted String
- Throws:
ArithmeticException
- if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY- See Also:
-
format
Specialization of format.- Parameters:
number
- the double number to formattoAppendTo
- the StringBuffer to which the formatted text is to be appendedpos
- keeps track on the position of the field within the returned string. For example, for formatting a number1234567.89
inLocale.US
locale, if the givenfieldPosition
isINTEGER_FIELD
, the begin index and end index offieldPosition
will be set to 0 and 9, respectively for the output string1,234,567.89
.- Returns:
- the formatted StringBuffer
- Throws:
ArithmeticException
- if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY- See Also:
-
format
Specialization of format.- Parameters:
number
- the long number to formattoAppendTo
- the StringBuffer to which the formatted text is to be appendedpos
- keeps track on the position of the field within the returned string. For example, for formatting a number123456789
inLocale.US
locale, if the givenfieldPosition
isINTEGER_FIELD
, the begin index and end index offieldPosition
will be set to 0 and 11, respectively for the output string123,456,789
.- Returns:
- the formatted StringBuffer
- Throws:
ArithmeticException
- if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY- See Also:
-
parse
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!- Parameters:
source
- the String to parseparsePosition
- the parse position- Returns:
- the parsed value
- See Also:
-
parse
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
parse(String, ParsePosition)
method for more information on number parsing.- Parameters:
source
- AString
whose beginning should be parsed.- Returns:
- A
Number
parsed from the string. - Throws:
ParseException
- if the beginning of the specified string cannot be parsed.
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isParseIntegerOnly
public boolean isParseIntegerOnly()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 dependent and determined by sub-classes of NumberFormat.- Returns:
true
if numbers should be parsed as integers only;false
otherwise
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setParseIntegerOnly
public void setParseIntegerOnly(boolean value) Sets whether or not numbers should be parsed as integers only.- Parameters:
value
-true
if numbers should be parsed as integers only;false
otherwise- See Also:
-
getInstance
Returns a general-purpose number format for the current defaultFORMAT
locale. This is the same as callinggetNumberInstance()
.- Returns:
- the
NumberFormat
instance for general-purpose number formatting
-
getInstance
Returns a general-purpose number format for the specified locale. This is the same as callinggetNumberInstance(inLocale)
.- Parameters:
inLocale
- the desired locale- Returns:
- the
NumberFormat
instance for general-purpose number formatting
-
getNumberInstance
Returns a general-purpose number format for the current defaultFORMAT
locale.This is equivalent to calling
getNumberInstance(Locale.getDefault(Locale.Category.FORMAT))
.- Returns:
- the
NumberFormat
instance for general-purpose number formatting - See Also:
-
getNumberInstance
Returns a general-purpose number format for the specified locale.- Parameters:
inLocale
- the desired locale- Returns:
- the
NumberFormat
instance for general-purpose number formatting
-
getIntegerInstance
Returns an integer number format for the current defaultFORMAT
locale. The returned number format is configured to round floating point numbers to the nearest integer using half-even rounding (seeRoundingMode.HALF_EVEN
) for formatting, and to parse only the integer part of an input string (seeisParseIntegerOnly
).This is equivalent to calling
getIntegerInstance(Locale.getDefault(Locale.Category.FORMAT))
.- Returns:
- a number format for integer values
- Since:
- 1.4
- See Also:
-
getIntegerInstance
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 half-even rounding (seeRoundingMode.HALF_EVEN
) for formatting, and to parse only the integer part of an input string (seeisParseIntegerOnly
).- Parameters:
inLocale
- the desired locale- Returns:
- a number format for integer values
- Since:
- 1.4
- See Also:
-
getCurrencyInstance
Returns a currency format for the current defaultFORMAT
locale.This is equivalent to calling
getCurrencyInstance(Locale.getDefault(Locale.Category.FORMAT))
.- Returns:
- the
NumberFormat
instance for currency formatting - See Also:
-
getCurrencyInstance
Returns a currency format for the specified locale.If the specified locale contains the "
cf
" ( currency format style) Unicode extension, the returned currency format uses the style if it is available. Otherwise, the style uses the default "standard
" currency format. For example, if the style designates "account
", negative currency amounts use a pair of parentheses in some locales.- Parameters:
inLocale
- the desired locale- Returns:
- the
NumberFormat
instance for currency formatting - External Specifications
-
getPercentInstance
Returns a percentage format for the current defaultFORMAT
locale.This is equivalent to calling
getPercentInstance(Locale.getDefault(Locale.Category.FORMAT))
.- Returns:
- the
NumberFormat
instance for percentage formatting - See Also:
-
getPercentInstance
Returns a percentage format for the specified locale.- Parameters:
inLocale
- the desired locale- Returns:
- the
NumberFormat
instance for percentage formatting
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getCompactNumberInstance
- Returns:
- A
NumberFormat
instance for compact number formatting - Since:
- 12
- See Also:
-
getCompactNumberInstance
Returns a compact number format for the specifiedlocale
andformatStyle
.- Parameters:
locale
- the desired localeformatStyle
- the style for formatting a number- Returns:
- A
NumberFormat
instance for compact number formatting - Throws:
NullPointerException
- iflocale
orformatStyle
isnull
- Since:
- 12
- See Also:
-
getAvailableLocales
Returns an array of all locales for which theget*Instance
methods of this class can return localized instances. The returned array represents the union of locales supported by the Java runtime and by installedNumberFormatProvider
implementations. At a minimum, the returned array must contain aLocale
instance equal toLocale.ROOT
and aLocale
instance equal toLocale.US
.- Returns:
- An array of locales for which localized
NumberFormat
instances are available.
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hashCode
public int hashCode()Returns the hash code for thisNumberFormat
.- Overrides:
hashCode
in classObject
- Implementation Requirements:
- This method calculates the hash code value using the values returned by
getMaximumIntegerDigits()
andgetMaximumFractionDigits()
. - Returns:
- the hash code for this
NumberFormat
- See Also:
-
equals
Compares the specified object with thisNumberFormat
for equality. Returns true if the object is also aNumberFormat
and the two formats would format any value the same.- Overrides:
equals
in classObject
- Implementation Requirements:
- This method performs an equality check with a notion of class
identity based on
getClass()
, rather thaninstanceof
. Therefore, in the equals methods in subclasses, no instance of this class should compare as equal to an instance of a subclass. - Parameters:
obj
- object to be compared for equality- Returns:
true
if the specified object is equal to thisNumberFormat
- See Also:
-
clone
-
isGroupingUsed
public boolean isGroupingUsed()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 dependent and is determined by sub-classes of NumberFormat.- Returns:
true
if grouping is used;false
otherwise- See Also:
-
setGroupingUsed
public void setGroupingUsed(boolean newValue) Set whether or not grouping will be used in this format.- Parameters:
newValue
-true
if grouping is used;false
otherwise- See Also:
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getMaximumIntegerDigits
public int getMaximumIntegerDigits()Returns the maximum number of digits allowed in the integer portion of a number.- Returns:
- the maximum number of digits
- See Also:
-
setMaximumIntegerDigits
public void setMaximumIntegerDigits(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.- Parameters:
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 Also:
-
getMinimumIntegerDigits
public int getMinimumIntegerDigits()Returns the minimum number of digits allowed in the integer portion of a number.- Returns:
- the minimum number of digits
- See Also:
-
setMinimumIntegerDigits
public void setMinimumIntegerDigits(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- Parameters:
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 Also:
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getMaximumFractionDigits
public int getMaximumFractionDigits()Returns the maximum number of digits allowed in the fraction portion of a number.- Returns:
- the maximum number of digits.
- See Also:
-
setMaximumFractionDigits
public void setMaximumFractionDigits(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.- Parameters:
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 Also:
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getMinimumFractionDigits
public int getMinimumFractionDigits()Returns the minimum number of digits allowed in the fraction portion of a number.- Returns:
- the minimum number of digits
- See Also:
-
setMinimumFractionDigits
public void setMinimumFractionDigits(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 maximumFractionDigits will also be set to the new value- Parameters:
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 Also:
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getCurrency
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 benull
if no valid currency could be determined and no currency has been set usingsetCurrency(Currency)
.- Implementation Requirements:
- The default implementation always throws
UnsupportedOperationException
. Subclasses should override this method if currency formatting is desired. - Returns:
- the currency used by this number format, or
null
- Throws:
UnsupportedOperationException
- if the implementation of this method does not support this operation- Since:
- 1.4
-
setCurrency
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.- Implementation Requirements:
- The default implementation always throws
UnsupportedOperationException
. Subclasses should override this method if currency formatting is desired. - Parameters:
currency
- the new currency to be used by this number format- Throws:
NullPointerException
- ifcurrency
isnull
UnsupportedOperationException
- if the implementation of this method does not support this operation- Since:
- 1.4
-
getRoundingMode
Gets theRoundingMode
used in this NumberFormat.- Implementation Requirements:
- The default implementation always throws
UnsupportedOperationException
. Subclasses which handle different rounding modes should override this method. - Returns:
- The
RoundingMode
used for this NumberFormat. - Throws:
UnsupportedOperationException
- if the implementation of this method does not support this operation- Since:
- 1.6
- See Also:
-
setRoundingMode
Sets theRoundingMode
used in this NumberFormat.- Implementation Requirements:
- The default implementation always throws
UnsupportedOperationException
. Subclasses which handle different rounding modes should override this method. - Parameters:
roundingMode
- TheRoundingMode
to be used- Throws:
NullPointerException
- ifroundingMode
isnull
UnsupportedOperationException
- if the implementation of this method does not support this operation- Since:
- 1.6
- See Also:
-