public class

NumberFormat

extends Object
java.lang.Object
   ↳ com.google.gwt.i18n.client.NumberFormat

Class Overview

Formats and parses numbers using locale-sensitive patterns. This class provides comprehensive and flexible support for a wide variety of localized formats, including

  • Locale-specific symbols such as decimal point, group separator, digit representation, currency symbol, percent, and permill
  • Numeric variations including integers ("123"), fixed-point numbers ("123.4"), scientific notation ("1.23E4"), percentages ("12%"), and currency amounts ("$123")
  • Predefined standard patterns that can be used both for parsing and formatting, including decimal, currency, percentages, and scientific
  • Custom patterns and supporting features designed to make it possible to parse and format numbers in any locale, including support for Western, Arabic, and Indic digits

Patterns

Formatting and parsing are based on customizable patterns that can include a combination of literal characters and special characters that act as placeholders and are replaced by their localized counterparts. 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. For example, the '#' character is replaced by a localized digit.

Often the replacement character is the same as the pattern character. In the U.S. locale, for example, the ',' grouping character is replaced by the same character ','. However, the replacement is still actually happening, and in a different locale, the grouping character may change to a different character, such as '.'. Some special characters affect the behavior of the formatter by their presence. For example, if the percent character is seen, then the value is multiplied by 100 before being displayed.

The characters listed below are used in patterns. Localized symbols use the corresponding characters taken from corresponding locale symbol collection, which can be found in the properties files residing in the com.google.gwt.i18n.client.constants. To insert a special character in a pattern as a literal (that is, without any special meaning) the character must be quoted. There are some exceptions to this which are noted below.

Symbol Location Localized? Meaning
0 Number 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
E Number 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
(\u2030) Prefix or suffix Yes Multiply by 1000 and show as per mille
¤ (\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 succession, such as "# o''clock"

A NumberFormat pattern contains a postive and negative subpattern separated by a semicolon, such as "#,##0.00;(#,##0.00)". Each subpattern has a prefix, a numeric part, and a suffix. If there is no explicit negative subpattern, the negative subpattern is the localized minus sign prefixed to the positive 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 ignored in the negative subpattern. That means that "#,##0.0#;(#)" has precisely the same result 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, the decimal separator and thousands separator should be distinct characters, or parsing will be impossible.

The grouping separator is a character that separates clusters of integer digits to make large numbers more legible. It commonly used for thousands, but in some locales it separates ten-thousands. The grouping size is the number of digits between the grouping separators, such as 3 for "100,000,000" or 4 for "1 0000 0000".

Pattern Grammar (BNF)

The pattern itself uses the following grammar:

pattern := subpattern (';' subpattern)?
subpattern := prefix? number exponent? suffix?
number := (integer ('.' fraction)?) | sigDigits
prefix := '\u0000'..'\uFFFD' - specialCharacters
suffix := '\u0000'..'\uFFFD' - specialCharacters
integer := '#'* '0'*'0'
fraction := '0'* '#'*
sigDigits := '#'* '@''@'* '#'*
exponent := 'E' '+'? '0'* '0'
padSpec := '*' padChar
padChar := '\u0000'..'\uFFFD' - quote

Notation:

X* 0 or more instances of X
X? 0 or 1 instances of X
X|Y either X or Y
C..D any character from C up to D, inclusive
S-T characters in S, except those in T

The first subpattern is for positive numbers. The second (optional) subpattern is for negative numbers.

Example

{@example com.google.gwt.examples.NumberFormatExample}

Summary

Fields
protected static NumberConstants defaultNumberConstants Current NumberConstants interface to use, see setForcedLatinDigits(boolean) for changing it.
protected static final NumberConstants localizedNumberConstants
Protected Constructors
NumberFormat(NumberConstants numberConstants, String pattern, CurrencyData cdata, boolean userSuppliedPattern)
Constructs a format object based on the specified settings.
NumberFormat(String pattern, CurrencyData cdata, boolean userSuppliedPattern)
Constructs a format object for the default locale based on the specified settings.
Public Methods
static boolean forcedLatinDigits()
Returns true if all new NumberFormat instances will use latin digits and related characters rather than the localized ones.
String format(Number number)
This method formats a Number to produce a string.
String format(double number)
This method formats a double to produce a string.
static NumberFormat getCurrencyFormat(String currencyCode)
Provides the standard currency format for the default locale using a specified currency.
static NumberFormat getCurrencyFormat(CurrencyData currencyData)
Provides the standard currency format for the default locale using a specified currency.
static NumberFormat getCurrencyFormat()
Provides the standard currency format for the default locale.
static NumberFormat getDecimalFormat()
Provides the standard decimal format for the default locale.
static NumberFormat getFormat(String pattern, String currencyCode)
Gets a custom NumberFormat instance for the default locale using the specified pattern and currency code.
static NumberFormat getFormat(String pattern, CurrencyData currencyData)
Gets a custom NumberFormat instance for the default locale using the specified pattern and currency code.
static NumberFormat getFormat(String pattern)
Gets a NumberFormat instance for the default locale using the specified pattern and the default currencyCode.
String getPattern()
Returns the pattern used by this number format.
static NumberFormat getPercentFormat()
Provides the standard percent format for the default locale.
static NumberFormat getScientificFormat()
Provides the standard scientific format for the default locale.
double parse(String text, int[] inOutPos)
Parses text to produce a numeric value.
double parse(String text)
Parses text to produce a numeric value.
static void setForcedLatinDigits(boolean useLatinDigits)
Specify whether all new NumberFormat instances will use latin digits and related characters rather than the localized ones.
Protected Methods
static NumberConstants createLatinNumberConstants(NumberConstants orig)
Create a delocalized NumberConstants instance from a localized one.
void format(boolean isNegative, StringBuilder digits, int scale)
Format a number with its significant digits already represented in string form.
String format(long value, int scale)
Format a possibly scaled long value.
int getGroupingSize()
Returns the number of digits between grouping separators in the integer portion of a number.
String getNegativePrefix()
Returns the prefix to use for negative values.
String getNegativeSuffix()
Returns the suffix to use for negative values.
NumberConstants getNumberConstants()
Returns the NumberConstants instance for this formatter.
String getPositivePrefix()
Returns the prefix to use for positive values.
String getPositiveSuffix()
Returns the suffix to use for positive values.
boolean isDecimalSeparatorAlwaysShown()
Returns true if the decimal separator should always be shown.
static String remapSeparator(String separator)
Remap a localized separator to an equivalent latin one.
[Expand]
Inherited Methods
From class java.lang.Object

Fields

protected static NumberConstants defaultNumberConstants

Current NumberConstants interface to use, see setForcedLatinDigits(boolean) for changing it.

protected static final NumberConstants localizedNumberConstants

Protected Constructors

protected NumberFormat (NumberConstants numberConstants, String pattern, CurrencyData cdata, boolean userSuppliedPattern)

Constructs a format object based on the specified settings.

Parameters
numberConstants the locale-specific number constants to use for this format -- **NOTE** subclasses passing their own instance here should pay attention to forcedLatinDigits() and remap localized symbols using createLatinNumberConstants(NumberConstants)
pattern pattern that specify how number should be formatted
cdata currency data that should be used
userSuppliedPattern true if the pattern was supplied by the user

protected NumberFormat (String pattern, CurrencyData cdata, boolean userSuppliedPattern)

Constructs a format object for the default locale based on the specified settings.

Parameters
pattern pattern that specify how number should be formatted
cdata currency data that should be used
userSuppliedPattern true if the pattern was supplied by the user

Public Methods

public static boolean forcedLatinDigits ()

Returns true if all new NumberFormat instances will use latin digits and related characters rather than the localized ones.

public String format (Number number)

This method formats a Number to produce a string.

Any Number which is not a BigDecimal, BigInteger, or Long instance is formatted as a double value.

Parameters
number The Number instance to format
Returns
  • the formatted number string

public String format (double number)

This method formats a double to produce a string.

Parameters
number The double to format
Returns
  • the formatted number string

public static NumberFormat getCurrencyFormat (String currencyCode)

Provides the standard currency format for the default locale using a specified currency.

Parameters
currencyCode valid currency code, as defined in com.google.gwt.i18n.client.constants.CurrencyCodeMapConstants.properties
Returns
  • a NumberFormat capable of producing and consuming currency format for the default locale
Throws
IllegalArgumentException if the currency code is unknown

public static NumberFormat getCurrencyFormat (CurrencyData currencyData)

Provides the standard currency format for the default locale using a specified currency.

Parameters
currencyData currency data to use
Returns
  • a NumberFormat capable of producing and consuming currency format for the default locale

public static NumberFormat getCurrencyFormat ()

Provides the standard currency format for the default locale.

Returns
  • a NumberFormat capable of producing and consuming currency format for the default locale

public static NumberFormat getDecimalFormat ()

Provides the standard decimal format for the default locale.

Returns
  • a NumberFormat capable of producing and consuming decimal format for the default locale

public static NumberFormat getFormat (String pattern, String currencyCode)

Gets a custom NumberFormat instance for the default locale using the specified pattern and currency code.

Parameters
pattern pattern for this formatter
currencyCode international currency code
Returns
  • a NumberFormat instance
Throws
IllegalArgumentException if the specified pattern is invalid or the currency code is unknown

public static NumberFormat getFormat (String pattern, CurrencyData currencyData)

Gets a custom NumberFormat instance for the default locale using the specified pattern and currency code.

Parameters
pattern pattern for this formatter
currencyData currency data
Returns
  • a NumberFormat instance
Throws
IllegalArgumentException if the specified pattern is invalid

public static NumberFormat getFormat (String pattern)

Gets a NumberFormat instance for the default locale using the specified pattern and the default currencyCode.

Parameters
pattern pattern for this formatter
Returns
  • a NumberFormat instance
Throws
IllegalArgumentException if the specified pattern is invalid

public String getPattern ()

Returns the pattern used by this number format.

public static NumberFormat getPercentFormat ()

Provides the standard percent format for the default locale.

Returns
  • a NumberFormat capable of producing and consuming percent format for the default locale

public static NumberFormat getScientificFormat ()

Provides the standard scientific format for the default locale.

Returns
  • a NumberFormat capable of producing and consuming scientific format for the default locale

public double parse (String text, int[] inOutPos)

Parses text to produce a numeric value.

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.

Parameters
text the string to be parsed
inOutPos position to pass in and get back
Returns
  • a double value representing the parsed number
Throws
NumberFormatException if the text segment could not be converted into a double

public double parse (String text)

Parses text to produce a numeric value. A NumberFormatException is thrown if either the text is empty or if the parse does not consume all characters of the text.

Parameters
text the string being parsed
Returns
  • a double value representing the parsed number
Throws
NumberFormatException if the entire text could not be converted into a double

public static void setForcedLatinDigits (boolean useLatinDigits)

Specify whether all new NumberFormat instances will use latin digits and related characters rather than the localized ones.

Parameters
useLatinDigits true if latin digits/etc should be used, false if localized digits/etc should be used.

Protected Methods

protected static NumberConstants createLatinNumberConstants (NumberConstants orig)

Create a delocalized NumberConstants instance from a localized one.

Parameters
orig localized NumberConstants instance
Returns
  • NumberConstants instance using latin digits/etc

protected void format (boolean isNegative, StringBuilder digits, int scale)

Format a number with its significant digits already represented in string form. This is done so both double and BigInteger/Decimal formatting can share code without requiring all users to pay the code size penalty for BigDecimal/etc.

Example values passed in:

  • -13e2
    isNegative=true, digits="13", scale=2
  • 3.14158
    isNegative=false, digits="314158", scale=-5
  • .0001
    isNegative=false, digits="1" ("0001" would be ok), scale=-4

Parameters
isNegative true if the value to be formatted is negative
digits a StringBuilder containing just the significant digits in the value to be formatted, the formatted result will be left here
scale the number of places to the right the decimal point should be moved in the digit string -- negative means the value contains fractional digits

protected String format (long value, int scale)

Format a possibly scaled long value.

Parameters
value value to format
scale the number of places to the right the decimal point should be moved in the digit string -- negative means the value contains fractional digits
Returns
  • formatted value

protected int getGroupingSize ()

Returns the number of digits between grouping separators in the integer portion of a number.

protected String getNegativePrefix ()

Returns the prefix to use for negative values.

protected String getNegativeSuffix ()

Returns the suffix to use for negative values.

protected NumberConstants getNumberConstants ()

Returns the NumberConstants instance for this formatter.

protected String getPositivePrefix ()

Returns the prefix to use for positive values.

protected String getPositiveSuffix ()

Returns the suffix to use for positive values.

protected boolean isDecimalSeparatorAlwaysShown ()

Returns true if the decimal separator should always be shown.

protected static String remapSeparator (String separator)

Remap a localized separator to an equivalent latin one.

Returns
  • delocalized separator character