Package com.google.gwt.i18n.client

Class NumberFormat

java.lang.Object
com.google.gwt.i18n.client.NumberFormat
public class NumberFormat extends Object
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

public class NumberFormatExample implements EntryPoint {

  public void onModuleLoad() {
    NumberFormat fmt = NumberFormat.getDecimalFormat();
    double value = 12345.6789;
    String formatted = fmt.format(value);
    // Prints 1,2345.6789 in the default locale
    GWT.log("Formatted string is" + formatted);

    // Turn a string back into a double
    value = NumberFormat.getDecimalFormat().parse("12345.6789");
    GWT.log("Parsed value is" + value);

    // Scientific notation
    value = 12345.6789;
    formatted = NumberFormat.getScientificFormat().format(value);
    // prints 1.2345E4 in the default locale
    GWT.log("Formatted string is" + formatted);

    // Currency
    fmt = NumberFormat.getCurrencyFormat();
    formatted = fmt.format(123456.7899);
    // prints US$123,456.79 in the default locale or $123,456.79 in the en_US
    // locale
    GWT.log("Formatted currency is" + formatted);
    
    // Custom format
    value = 12345.6789;
    formatted = NumberFormat.getFormat("000000.000000").format(value);
    // prints 012345.678900 in the default locale
    GWT.log("Formatted string is" + formatted);
  }
}

  • Field Details

  • Constructor Details

    • NumberFormat

      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

    • NumberFormat

      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

  • Method Details

    • forcedLatinDigits

      public static boolean forcedLatinDigits()
      Returns true if all new NumberFormat instances will use latin digits and related characters rather than the localized ones.

    • getCurrencyFormat

      public static NumberFormat getCurrencyFormat()
      Provides the standard currency format for the current locale.
      Returns:
      a NumberFormat capable of producing and consuming currency format for the default locale

    • getCurrencyFormat

      public static NumberFormat getCurrencyFormat(CurrencyData currencyData)
      Provides the standard currency format for the current locale using a specified currency.
      Parameters:
      currencyData - currency data to use
      Returns:
      a NumberFormat capable of producing and consuming currency format for the current locale

    • getCurrencyFormat

      public static NumberFormat getCurrencyFormat(String currencyCode)
      Provides the standard currency format for the current 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 current locale
      Throws:
      IllegalArgumentException - if the currency code is unknown

    • getDecimalFormat

      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

    • getFormat

      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

    • getFormat

      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

    • getFormat

      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

    • getGlobalCurrencyFormat

      public static NumberFormat getGlobalCurrencyFormat()
      Provides the global currency format for the current locale, using its default currency.
      Returns:
      a NumberFormat capable of producing and consuming currency format for the current locale

    • getGlobalCurrencyFormat

      public static NumberFormat getGlobalCurrencyFormat(CurrencyData currencyData)
      Provides the global currency format for the current locale, using a specified currency.
      Parameters:
      currencyData - currency data to use
      Returns:
      a NumberFormat capable of producing and consuming currency format for the current locale

    • getGlobalCurrencyFormat

      public static NumberFormat getGlobalCurrencyFormat(String currencyCode)
      Provides the global currency format for the current 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 current locale
      Throws:
      IllegalArgumentException - if the currency code is unknown

    • getPercentFormat

      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

    • getScientificFormat

      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

    • getSimpleCurrencyFormat

      public static NumberFormat getSimpleCurrencyFormat()
      Provides the simple currency format for the current locale using its default currency. Note that these formats may be ambiguous if the currency isn't clear from other content on the page.
      Returns:
      a NumberFormat capable of producing and consuming currency format for the current locale

    • getSimpleCurrencyFormat

      public static NumberFormat getSimpleCurrencyFormat(CurrencyData currencyData)
      Provides the simple currency format for the current locale using a specified currency. Note that these formats may be ambiguous if the currency isn't clear from other content on the page.
      Parameters:
      currencyData - currency data to use
      Returns:
      a NumberFormat capable of producing and consuming currency format for the current locale

    • getSimpleCurrencyFormat

      public static NumberFormat getSimpleCurrencyFormat(String currencyCode)
      Provides the simple currency format for the current locale using a specified currency. Note that these formats may be ambiguous if the currency isn't clear from other content on the page.
      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 current locale
      Throws:
      IllegalArgumentException - if the currency code is unknown

    • setForcedLatinDigits

      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.

    • createLatinNumberConstants

      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

    • remapSeparator

      protected static String remapSeparator(String separator)
      Remap a localized separator to an equivalent latin one.
      Parameters:
      separator -
      Returns:
      delocalized separator character

    • toScaledString

      static int toScaledString(StringBuilder buf, double val)
      Appends a scaled string representation to a buffer, returning the scale (which is the number of places to the right of the end of the string the decimal point should be moved -- i.e., 3.5 would be added to the buffer as "35" and a returned scale of -1).
      Parameters:
      buf -
      val -
      Returns:
      scale to apply to the result

    • format

      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

    • format

      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

    • getPattern

      public String getPattern()
      Returns the pattern used by this number format.

    • overrideFractionDigits

      public NumberFormat overrideFractionDigits(int digits)
      Change the number of fractional digits used for formatting with this instance.
      Parameters:
      digits - the exact number of fractional digits for formatted values; must be >= 0
      Returns:
      this, for chaining purposes

    • overrideFractionDigits

      public NumberFormat overrideFractionDigits(int minDigits, int maxDigits)
      Change the number of fractional digits used for formatting with this instance. Digits after minDigits that are zero will be omitted from the formatted value.
      Parameters:
      minDigits - the minimum number of fractional digits for formatted values; must be >= 0
      maxDigits - the maximum number of fractional digits for formatted values; must be >= minDigits
      Returns:
      this, for chaining purposes

    • parse

      public double parse(String text) throws NumberFormatException
      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

    • parse

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

    • format

      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

    • format

      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

    • getGroupingSize

      protected int getGroupingSize()
      Returns the number of digits between grouping separators in the integer portion of a number.

    • getNegativePrefix

      protected String getNegativePrefix()
      Returns the prefix to use for negative values.

    • getNegativeSuffix

      protected String getNegativeSuffix()
      Returns the suffix to use for negative values.

    • getNumberConstants

      protected NumberConstants getNumberConstants()
      Returns the NumberConstants instance for this formatter.

    • getPositivePrefix

      protected String getPositivePrefix()
      Returns the prefix to use for positive values.

    • getPositiveSuffix

      protected String getPositiveSuffix()
      Returns the suffix to use for positive values.

    • isDecimalSeparatorAlwaysShown

      protected boolean isDecimalSeparatorAlwaysShown()
      Returns true if the decimal separator should always be shown.