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java.text
public class: DecimalFormat [javadoc | source]
java.lang.Object
   java.text.Format
      java.text.NumberFormat
         java.text.DecimalFormat

All Implemented Interfaces:
    Cloneable, Serializable

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".

Rounding

DecimalFormat provides rounding modes defined in java.math.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

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) {}
    }
}
Field Summary
static final  int currentSerialVersion     
static final  int DOUBLE_INTEGER_DIGITS     
static final  int DOUBLE_FRACTION_DIGITS     
static final  int MAXIMUM_INTEGER_DIGITS     
static final  int MAXIMUM_FRACTION_DIGITS     
static final  long serialVersionUID     
Fields inherited from java.text.NumberFormat:
INTEGER_FIELD,  FRACTION_FIELD,  currentSerialVersion,  serialVersionUID
Constructor:
 public DecimalFormat() 
 public DecimalFormat(String pattern) 
    Creates a DecimalFormat using the given pattern and the symbols for the default locale. This is a convenient way to obtain a DecimalFormat when internationalization is not the main concern.

    To obtain standard formats for a given locale, use the factory methods on NumberFormat such as getNumberInstance. These factories will return the most appropriate sub-class of NumberFormat for a given locale.

    Parameters:
    pattern - A non-localized pattern string.
    Throws:
    NullPointerException - if pattern is null
    IllegalArgumentException - if the given pattern is invalid.
    Also see:
    java.text.NumberFormat#getInstance
    java.text.NumberFormat#getNumberInstance
    java.text.NumberFormat#getCurrencyInstance
    java.text.NumberFormat#getPercentInstance
    exception: NullPointerException - if pattern is null
    exception: IllegalArgumentException - if the given pattern is invalid.
 public DecimalFormat(String pattern,
    DecimalFormatSymbols symbols) 
    Creates a DecimalFormat using the given pattern and symbols. Use this constructor when you need to completely customize the behavior of the format.

    To obtain standard formats for a given locale, use the factory methods on NumberFormat such as getInstance or getCurrencyInstance. If you need only minor adjustments to a standard format, you can modify the format returned by a NumberFormat factory method.

    Parameters:
    pattern - a non-localized pattern string
    symbols - the set of symbols to be used
    Throws:
    NullPointerException - if any of the given arguments is null
    IllegalArgumentException - if the given pattern is invalid
    Also see:
    java.text.NumberFormat#getInstance
    java.text.NumberFormat#getNumberInstance
    java.text.NumberFormat#getCurrencyInstance
    java.text.NumberFormat#getPercentInstance
    java.text.DecimalFormatSymbols
    exception: NullPointerException - if any of the given arguments is null
    exception: IllegalArgumentException - if the given pattern is invalid
Method from java.text.DecimalFormat Summary:
adjustForCurrencyDefaultFractionDigits,   applyLocalizedPattern,   applyPattern,   clone,   equals,   format,   format,   format,   formatToCharacterIterator,   getCurrency,   getDecimalFormatSymbols,   getGroupingSize,   getMaximumFractionDigits,   getMaximumIntegerDigits,   getMinimumFractionDigits,   getMinimumIntegerDigits,   getMultiplier,   getNegativePrefix,   getNegativeSuffix,   getPositivePrefix,   getPositiveSuffix,   getRoundingMode,   hashCode,   isDecimalSeparatorAlwaysShown,   isParseBigDecimal,   parse,   setCurrency,   setDecimalFormatSymbols,   setDecimalSeparatorAlwaysShown,   setGroupingSize,   setMaximumFractionDigits,   setMaximumIntegerDigits,   setMinimumFractionDigits,   setMinimumIntegerDigits,   setMultiplier,   setNegativePrefix,   setNegativeSuffix,   setParseBigDecimal,   setPositivePrefix,   setPositiveSuffix,   setRoundingMode,   toLocalizedPattern,   toPattern
Methods from java.text.NumberFormat:
clone,   equals,   format,   format,   format,   format,   format,   getAvailableLocales,   getCurrency,   getCurrencyInstance,   getCurrencyInstance,   getInstance,   getInstance,   getIntegerInstance,   getIntegerInstance,   getMaximumFractionDigits,   getMaximumIntegerDigits,   getMinimumFractionDigits,   getMinimumIntegerDigits,   getNumberInstance,   getNumberInstance,   getPercentInstance,   getPercentInstance,   getRoundingMode,   getScientificInstance,   getScientificInstance,   hashCode,   isGroupingUsed,   isParseIntegerOnly,   parse,   parse,   parseObject,   setCurrency,   setGroupingUsed,   setMaximumFractionDigits,   setMaximumIntegerDigits,   setMinimumFractionDigits,   setMinimumIntegerDigits,   setParseIntegerOnly,   setRoundingMode
Methods from java.text.Format:
clone,   createAttributedCharacterIterator,   createAttributedCharacterIterator,   createAttributedCharacterIterator,   createAttributedCharacterIterator,   format,   format,   formatToCharacterIterator,   parseObject,   parseObject
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from java.text.DecimalFormat Detail:
  void adjustForCurrencyDefaultFractionDigits() 
    Adjusts the minimum and maximum fraction digits to values that are reasonable for the currency's default fraction digits.
 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.

 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.

 public Object clone() 
    Standard override; no change in semantics.
 public boolean equals(Object obj) 
    Overrides equals
 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 java.lang.Number .

    This implementation uses the maximum precision permitted.

 public StringBuffer format(double number,
    StringBuffer result,
    FieldPosition fieldPosition) 
    Formats a double to produce a string.
 public StringBuffer format(long number,
    StringBuffer result,
    FieldPosition fieldPosition) 
    Format a long to produce a string.
 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.

 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.
 public DecimalFormatSymbols getDecimalFormatSymbols() 
    Returns a copy of the decimal format symbols, which is generally not changed by the programmer or user.
 public int getGroupingSize() 
    Return the grouping size. Grouping size is the number of digits between grouping separators in the integer portion of a number. For example, in the number "123,456.78", the grouping size is 3.
 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.
 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.
 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.
 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.
 public int getMultiplier() 
    Gets the multiplier for use in percent, per mille, and similar formats.
 public String getNegativePrefix() 
    Get the negative prefix.

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

 public String getNegativeSuffix() 
    Get the negative suffix.

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

 public String getPositivePrefix() 
    Get the positive prefix.

    Examples: +123, $123, sFr123

 public String getPositiveSuffix() 
    Get the positive suffix.

    Example: 123%

 public RoundingMode getRoundingMode() 
 public int hashCode() 
    Overrides hashCode
 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

 public boolean isParseBigDecimal() 
 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 java.math.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.

 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.
 public  void setDecimalFormatSymbols(DecimalFormatSymbols newSymbols) 
    Sets the decimal format symbols, which is generally not changed by the programmer or user.
 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

 public  void setGroupingSize(int newValue) 
    Set the grouping size. Grouping size is the number of digits between grouping separators in the integer portion of a number. For example, in the number "123,456.78", the grouping size is 3.
    The value passed in is converted to a byte, which may lose information.
 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.
 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.
 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.
 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.
 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.

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

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

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

    Examples: 123%

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

    Examples: +123, $123, sFr123

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

    Example: 123%

 public  void setRoundingMode(RoundingMode roundingMode) 
 public String toLocalizedPattern() 
    Synthesizes a localized pattern string that represents the current state of this Format object.
 public String toPattern() 
    Synthesizes a pattern string that represents the current state of this Format object.