java.text

Class DecimalFormat

Table des matières
  • All Implemented Interfaces:
    Serializable, Cloneable

    public class DecimalFormat
extends NumberFormat
    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.

    Patterns

    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 "#,##,###,####" == "######,####" == "##,####,####".

    Special Pattern Characters

    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
    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 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".

      

    Scientific Notation

    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".

    • The number of digit characters after the exponent character gives the minimum exponent digit count. There is no maximum. Negative exponents are formatted using the localized minus sign, not the prefix and suffix from the pattern. This allows patterns such as "0.###E0 m/s".
    • The minimum and maximum number of integer digits are interpreted together:
      • If the maximum number of integer digits is greater than their minimum number and greater than 1, it forces the exponent to be a multiple of the maximum number of integer digits, and the minimum number of integer digits to be interpreted as 1. The most common use of this is to generate engineering notation, in which the exponent is a multiple of three, e.g., "##0.#####E0". Using this pattern, the number 12345 formats to "12.345E3", and 123456 formats to "123.456E3".
      • Otherwise, the minimum number of integer digits is achieved by adjusting the exponent. Example: 0.00123 formatted with "00.###E0" yields "12.3E-4".
    • The number of significant digits in the mantissa is the sum of the minimum integer and maximum fraction digits, and is unaffected by the maximum integer digits. For example, 12345 formatted with "##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.
    • Exponential patterns may not contain grouping separators.

    Rounding

    DecimalFormat provides rounding modes defined in RoundingMode for formatting. By default, it uses RoundingMode.HALF_EVEN.

    Digits

    For formatting, 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.

    Special Values

    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.

    Synchronization

    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.

    Example

     // 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) {}
     }
 }
    See Also:
    Java Tutorial, NumberFormat, DecimalFormatSymbols, ParsePosition, Serialized Form

    • Method Detail

      • format

        public final StringBuffer format(Object number,
                  StringBuffer toAppendTo,
                  FieldPosition pos)
        Formats a number and appends the resulting text to the given string buffer. The number can be of any subclass of Number.

        This implementation uses the maximum precision permitted.

        Overrides:
        format in class NumberFormat
        Parameters:
        number - the number to format
        toAppendTo - the StringBuffer to which the formatted text is to be appended
        pos - On input: an alignment field, if desired. On output: the offsets of the alignment field.
        Returns:
        the value passed in as toAppendTo
        Throws:
        IllegalArgumentException - if number is null or not an instance of Number.
        NullPointerException - if toAppendTo or pos is null
        ArithmeticException - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY
        See Also:
        FieldPosition

      • format

        public StringBuffer format(double number,
                  StringBuffer result,
                  FieldPosition fieldPosition)
        Formats a double to produce a string.
        Specified by:
        format in class NumberFormat
        Parameters:
        number - The double to format
        result - where the text is to be appended
        fieldPosition - On input: an alignment field, if desired. On output: the offsets of the alignment field.
        Returns:
        The formatted number string
        Throws:
        ArithmeticException - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY
        See Also:
        FieldPosition

      • format

        public StringBuffer format(long number,
                  StringBuffer result,
                  FieldPosition fieldPosition)
        Format a long to produce a string.
        Specified by:
        format in class NumberFormat
        Parameters:
        number - The long to format
        result - where the text is to be appended
        fieldPosition - On input: an alignment field, if desired. On output: the offsets of the alignment field.
        Returns:
        The formatted number string
        Throws:
        ArithmeticException - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY
        See Also:
        FieldPosition

      • formatToCharacterIterator

        public AttributedCharacterIterator formatToCharacterIterator(Object obj)
        Formats an Object producing an AttributedCharacterIterator. 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.

        Overrides:
        formatToCharacterIterator in class Format
        Parameters:
        obj - The object to format
        Returns:
        AttributedCharacterIterator describing the formatted value.
        Throws:
        NullPointerException - if obj is null.
        IllegalArgumentException - when the Format cannot format the given object.
        ArithmeticException - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY
        Since:
        1.4

      • parse

        public Number parse(String 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.

        The subclass returned depends on the value of isParseBigDecimal() as well as on the string being parsed.

        • If 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.

        • If isParseBigDecimal() is true, values are returned as BigDecimal objects. The values are the ones constructed by BigDecimal.BigDecimal(String) for corresponding strings in locale-independent format. The special cases negative and positive infinity and NaN are returned as 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.

        Specified by:
        parse in class NumberFormat
        Parameters:
        text - the string to be parsed
        pos - A ParsePosition object with index and error index information as described above.
        Returns:
        the parsed value, or null if the parse fails
        Throws:
        NullPointerException - if text or pos is null.
        See Also:
        NumberFormat.isParseIntegerOnly(), Format.parseObject(java.lang.String, java.text.ParsePosition)

      • getDecimalFormatSymbols

        public DecimalFormatSymbols getDecimalFormatSymbols()
        Returns a copy of the decimal format symbols, which is generally not changed by the programmer or user.
        Returns:
        a copy of the desired DecimalFormatSymbols
        See Also:
        DecimalFormatSymbols

      • setDecimalFormatSymbols

        public void setDecimalFormatSymbols(DecimalFormatSymbols newSymbols)
        Sets the decimal format symbols, which is generally not changed by the programmer or user.
        Parameters:
        newSymbols - desired DecimalFormatSymbols
        See Also:
        DecimalFormatSymbols

      • getPositivePrefix

        public String getPositivePrefix()
        Get the positive prefix.

        Examples: +123, $123, sFr123

      • setPositivePrefix

        public void setPositivePrefix(String newValue)
        Set the positive prefix.

        Examples: +123, $123, sFr123

      • getNegativePrefix

        public String getNegativePrefix()
        Get the negative prefix.

        Examples: -123, ($123) (with negative suffix), sFr-123

      • setNegativePrefix

        public void setNegativePrefix(String newValue)
        Set the negative prefix.

        Examples: -123, ($123) (with negative suffix), sFr-123

      • getPositiveSuffix

        public String getPositiveSuffix()
        Get the positive suffix.

        Example: 123%

      • setPositiveSuffix

        public void setPositiveSuffix(String newValue)
        Set the positive suffix.

        Example: 123%

      • getNegativeSuffix

        public String getNegativeSuffix()
        Get the negative suffix.

        Examples: -123%, ($123) (with positive suffixes)

      • setNegativeSuffix

        public void setNegativeSuffix(String newValue)
        Set the negative suffix.

        Examples: 123%

      • getMultiplier

        public int getMultiplier()
        Gets the multiplier for use in percent, per mille, and similar formats.
        See Also:
        setMultiplier(int)

      • setMultiplier

        public void setMultiplier(int newValue)
        Sets the multiplier for use in percent, per mille, and similar formats. For a percent format, set the multiplier to 100 and the suffixes to have '%' (for Arabic, use the Arabic percent sign). For a per mille format, set the multiplier to 1000 and the suffixes to have '\u2030'.

        Example: with multiplier 100, 1.23 is formatted as "123", and "123" is parsed into 1.23.

        See Also:
        getMultiplier()

      • isDecimalSeparatorAlwaysShown

        public boolean isDecimalSeparatorAlwaysShown()
        Allows you to get the behavior of the decimal separator with integers. (The decimal separator will always appear with decimals.)

        Example: Decimal ON: 12345 -> 12345.; OFF: 12345 -> 12345

      • setDecimalSeparatorAlwaysShown

        public void setDecimalSeparatorAlwaysShown(boolean newValue)
        Allows you to set the behavior of the decimal separator with integers. (The decimal separator will always appear with decimals.)

        Example: Decimal ON: 12345 -> 12345.; OFF: 12345 -> 12345

      • clone

        public Object clone()
        Standard override; no change in semantics.
        Overrides:
        clone in class NumberFormat
        Returns:
        a clone of this instance.
        See Also:
        Cloneable

      • equals

        public boolean equals(Object obj)
        Overrides equals
        Overrides:
        equals in class NumberFormat
        Parameters:
        obj - the reference object with which to compare.
        Returns:
        true if this object is the same as the obj argument; false otherwise.
        See Also:
        Object.hashCode(), HashMap

      • toLocalizedPattern

        public String toLocalizedPattern()
        Synthesizes a localized pattern string that represents the current state of this Format object.
        See Also:
        applyPattern(java.lang.String)

      • applyPattern

        public void applyPattern(String pattern)
        Apply the given pattern to this Format object. A pattern is a short-hand specification for the various formatting properties. These properties can also be changed individually through the various setter methods.

        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.

        Throws:
        NullPointerException - if pattern is null
        IllegalArgumentException - if the given pattern is invalid.

      • applyLocalizedPattern

        public void applyLocalizedPattern(String pattern)
        Apply the given pattern to this Format object. The pattern is assumed to be in a localized notation. A pattern is a short-hand specification for the various formatting properties. These properties can also be changed individually through the various setter methods.

        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.

        Throws:
        NullPointerException - if pattern is null
        IllegalArgumentException - if the given pattern is invalid.

      • setMaximumIntegerDigits

        public void setMaximumIntegerDigits(int newValue)
        Sets the maximum number of digits allowed in the integer portion of a number. For formatting numbers other than BigInteger and BigDecimal objects, the lower of newValue and 309 is used. Negative input values are replaced with 0.
        Overrides:
        setMaximumIntegerDigits in class NumberFormat
        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:
        NumberFormat.setMaximumIntegerDigits(int)

      • setMinimumIntegerDigits

        public void setMinimumIntegerDigits(int newValue)
        Sets the minimum number of digits allowed in the integer portion of a number. For formatting numbers other than BigInteger and BigDecimal objects, the lower of newValue and 309 is used. Negative input values are replaced with 0.
        Overrides:
        setMinimumIntegerDigits in class NumberFormat
        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:
        NumberFormat.setMinimumIntegerDigits(int)

      • setMaximumFractionDigits

        public void setMaximumFractionDigits(int newValue)
        Sets the maximum number of digits allowed in the fraction portion of a number. For formatting numbers other than BigInteger and BigDecimal objects, the lower of newValue and 340 is used. Negative input values are replaced with 0.
        Overrides:
        setMaximumFractionDigits in class NumberFormat
        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:
        NumberFormat.setMaximumFractionDigits(int)

      • setMinimumFractionDigits

        public void setMinimumFractionDigits(int newValue)
        Sets the minimum number of digits allowed in the fraction portion of a number. For formatting numbers other than BigInteger and BigDecimal objects, the lower of newValue and 340 is used. Negative input values are replaced with 0.
        Overrides:
        setMinimumFractionDigits in class NumberFormat
        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:
        NumberFormat.setMinimumFractionDigits(int)

      • getMaximumIntegerDigits

        public int getMaximumIntegerDigits()
        Gets the maximum number of digits allowed in the integer portion of a number. For formatting numbers other than BigInteger and BigDecimal objects, the lower of the return value and 309 is used.
        Overrides:
        getMaximumIntegerDigits in class NumberFormat
        See Also:
        setMaximumIntegerDigits(int)

      • getMinimumIntegerDigits

        public int getMinimumIntegerDigits()
        Gets the minimum number of digits allowed in the integer portion of a number. For formatting numbers other than BigInteger and BigDecimal objects, the lower of the return value and 309 is used.
        Overrides:
        getMinimumIntegerDigits in class NumberFormat
        See Also:
        setMinimumIntegerDigits(int)

      • getMaximumFractionDigits

        public int getMaximumFractionDigits()
        Gets the maximum number of digits allowed in the fraction portion of a number. For formatting numbers other than BigInteger and BigDecimal objects, the lower of the return value and 340 is used.
        Overrides:
        getMaximumFractionDigits in class NumberFormat
        See Also:
        setMaximumFractionDigits(int)

      • getMinimumFractionDigits

        public int getMinimumFractionDigits()
        Gets the minimum number of digits allowed in the fraction portion of a number. For formatting numbers other than BigInteger and BigDecimal objects, the lower of the return value and 340 is used.
        Overrides:
        getMinimumFractionDigits in class NumberFormat
        See Also:
        setMinimumFractionDigits(int)

      • getCurrency

        public Currency getCurrency()
        Gets the currency used by this decimal format when formatting currency values. The currency is obtained by calling DecimalFormatSymbols.getCurrency on this number format's symbols.
        Overrides:
        getCurrency in class NumberFormat
        Returns:
        the currency used by this decimal format, or null
        Since:
        1.4

      • setCurrency

        public void setCurrency(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 currency is set by calling DecimalFormatSymbols.setCurrency on this number format's symbols.
        Overrides:
        setCurrency in class NumberFormat
        Parameters:
        currency - the new currency to be used by this decimal format
        Throws:
        NullPointerException - if currency is null
        Since:
        1.4

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Document créé le 30/08/2006, dernière modification le 04/03/2020
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