Java Doc for DecimalFormat.java in  » 6.0-JDK-Core » text » java » text » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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

 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

Digits

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) {}
 }
 }
 

To obtain standard formats for a given locale, use the factory methods on NumberFormat such as getInstance or getCurrencyInstance.

This implementation uses the maximum precision permitted.
Parameters:
  number - the number to format
Parameters:
  toAppendTo - the StringBuffer to which the formattedtext is to be appended
Parameters:
  pos - On input: an alignment field, if desired.On output: the offsets of the alignment field.

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.

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.
See Also:   java.text.NumberFormat.getInstance
See Also:   java.text.NumberFormat.getNumberInstance
See Also:   java.text.NumberFormat.getCurrencyInstance
See Also:   java.text.NumberFormat.getPercentInstance

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.
exception:
  NullPointerException - if pattern is null
exception:
  IllegalArgumentException - if the given pattern is invalid.
See Also:   java.text.NumberFormat.getInstance
See Also:   java.text.NumberFormat.getNumberInstance
See Also:   java.text.NumberFormat.getCurrencyInstance
See Also:   java.text.NumberFormat.getPercentInstance

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
Parameters:
  symbols - the set of symbols to be used
exception:
  NullPointerException - if any of the given arguments is null
exception:
  IllegalArgumentException - if the given pattern is invalid
See Also:   java.text.NumberFormat.getInstance
See Also:   java.text.NumberFormat.getNumberInstance
See Also:   java.text.NumberFormat.getCurrencyInstance
See Also:   java.text.NumberFormat.getPercentInstance
See Also:   java.text.DecimalFormatSymbols

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

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

This implementation uses the maximum precision permitted.
Parameters:
  number - the number to format
Parameters:
  toAppendTo - the StringBuffer to which the formattedtext is to be appended
Parameters:
  pos - On input: an alignment field, if desired.On output: the offsets of the alignment field. the value passed in as toAppendTo
exception:
  IllegalArgumentException - if number isnull or not an instance of Number.
exception:
  NullPointerException - if toAppendTo or pos is null
exception:
  ArithmeticException - if rounding is needed with roundingmode being set to RoundingMode.UNNECESSARY
See Also:   java.text.FieldPosition

Each attribute key of the AttributedCharacterIterator will be of type NumberFormat.Field, with the attribute value being the same as the attribute key.
exception:
  NullPointerException - if obj is null.
exception:
  IllegalArgumentException - when the Format cannot format thegiven object.
exception:
  ArithmeticException - if rounding is needed with roundingmode being set to RoundingMode.UNNECESSARY
Parameters:
  obj - The object to format AttributedCharacterIterator describing the formatted value.
since:
   1.4

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

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

Examples: +123, $123, sFr123

Example: 123%

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

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 DecimalFormat.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.
Parameters:
  text - the string to be parsed
Parameters:
  pos - A ParsePosition object with index and errorindex information as described above. the parsed value, or null if the parse fails
exception:
  NullPointerException - if text orpos is null.

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

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

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

Examples: 123%

Examples: +123, $123, sFr123

Example: 123%