java.lang.Object java.text.Format java.text.NumberFormat java.text.DecimalFormat
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.
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
('-'
(code>'-'
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 "#,##,###,####" == "######,####" == "##,####,####".
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 ¤ (\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".
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".
NaN is formatted as a single character, typically \uFFFD. This character 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 single character, typically \u221E, with the positive or negative prefixes and suffixes applied. The infinity character is determined by the DecimalFormatSymbols object.
Negative zero ("-0") parses to
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.
// 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) {} } }
Nested Class Summary |
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Nested classes inherited from class java.text. NumberFormat |
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NumberFormat.Field |
Field Summary |
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Fields inherited from class java.text. NumberFormat |
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FRACTION_FIELD , INTEGER_FIELD |
Constructor Summary | |
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DecimalFormat
() Creates a DecimalFormat using the default pattern and symbols for the default locale. |
|
DecimalFormat
(
String
pattern) Creates a DecimalFormat using the given pattern and the symbols for the default locale. |
|
DecimalFormat
(
String
pattern,
DecimalFormatSymbols
symbols) Creates a DecimalFormat using the given pattern and symbols. |
Method Summary | |
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void |
applyLocalizedPattern
(
String
pattern) Apply the given pattern to this Format object. |
void |
applyPattern
(
String
pattern) Apply the given pattern to this Format object. |
Object |
clone
() Standard override; no change in semantics. |
boolean |
equals
(
Object
obj) Overrides equals |
StringBuffer |
format
(double number,
StringBuffer
result,
FieldPosition
fieldPosition) Formats a double to produce a string. |
StringBuffer |
format
(long number,
StringBuffer
result,
FieldPosition
fieldPosition) Format a long to produce a string. |
StringBuffer |
format
(
Object
number,
StringBuffer
toAppendTo,
FieldPosition
Formats a number and appends the resulting text to the given string buffer. |
AttributedCharacterIterator |
formatToCharacterIterator
(
Object
obj) Formats an Object producing an AttributedCharacterIterator. |
Currency |
getCurrency
() Gets the currency used by this decimal format when formatting currency values. |
DecimalFormatSymbols |
getDecimalFormatSymbols
() Returns the decimal format symbols, which is generally not changed by the programmer or user. |
int |
getGroupingSize
() Return the grouping size. |
int |
getMaximumFractionDigits
()
Gets the maximum number of digits allowed in the fraction portion of a number. |
int |
getMaximumIntegerDigits
()
Gets the maximum number of digits allowed in the integer portion of a number. |
int |
getMinimumFractionDigits
()
Gets the minimum number of digits allowed in the fraction portion of a number. |
int |
getMinimumIntegerDigits
()
Gets the minimum number of digits allowed in the integer portion of a number. |
int |
getMultiplier
() Get the multiplier for use in percent, permill, etc. |
String |
getNegativePrefix
() Get the negative prefix. |
String |
getNegativeSuffix
() Get the negative suffix. |
String |
getPositivePrefix
() Get the positive prefix. |
String |
getPositiveSuffix
() Get the positive suffix. |
int |
hashCode
() Overrides hashCode |
boolean |
isDecimalSeparatorAlwaysShown
() Allows you to get the behavior of the decimal separator with integers. |
boolean |
isParseBigDecimal
()
Returns whether the parse(java.lang.String, java.text.ParsePosition) |
Number |
parse
(
String
text,
ParsePosition
pos) Parses text from a string to produce a Number. |
void |
setCurrency
(
Currency
currency) Sets the currency used by this number format when formatting currency values. |
void |
setDecimalFormatSymbols
(
DecimalFormatSymbols
newSymbols) Sets the decimal format symbols, which is generally not changed by the programmer or user. |
void |
setDecimalSeparatorAlwaysShown
(boolean newValue) Allows you to set the behavior of the decimal separator with integers. |
void |
setGroupingSize
(int newValue) Set the grouping size. |
void |
setMaximumFractionDigits
(int newValue) Sets the maximum number of digits allowed in the fraction portion of a number. |
void |
setMaximumIntegerDigits
(int newValue) Sets the maximum number of digits allowed in the integer portion of a number. |
void |
setMinimumFractionDigits
(int newValue) Sets the minimum number of digits allowed in the fraction portion of a number. |
void |
setMinimumIntegerDigits
(int newValue) Sets the minimum number of digits allowed in the integer portion of a number. |
void |
setMultiplier
(int newValue) Set the multiplier for use in percent, permill, etc. |
void |
setNegativePrefix
(
String
newValue) Set the negative prefix. |
void |
setNegativeSuffix
(
String
Set the negative |
void |
setParseBigDecimal
(boolean newValue)
Sets whether the parse(java.lang.String, java.text.ParsePosition) |
void |
setPositivePrefix
(
String
newValue) Set the positive prefix. |
void |
setPositiveSuffix
(
String
newValue) Set the positive suffix. |
String |
toLocalizedPattern
() Synthesizes a localized pattern string that represents the current state of this Format object. |
String |
toPattern
() Synthesizes a pattern string that represents the current state of this Format object. |
Methods inherited from class java.text. NumberFormat |
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format
,
format
,
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Methods inherited from class java.text. Format |
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format , parseObject |
Methods inherited from class java.lang. Object |
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finalize , getClass , notify , notifyAll , toString , wait , wait , wait |
Constructor Detail |
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public DecimalFormat()
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.
public DecimalFormat(String pattern)
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.
public DecimalFormat(String pattern, DecimalFormatSymbols symbols)
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.
Method Detail |
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public final StringBufferformat ( Object number, StringBuffer toAppendTo, FieldPosition pos)
This implementation uses the maximum precision permitted.
public StringBuffer format(double number, StringBuffer result, FieldPosition fieldPosition)
public StringBuffer format(long number, StringBuffer result, FieldPosition fieldPosition)
public AttributedCharacterIterator formatToCharacterIterator(Object obj)
Each attribute key of the AttributedCharacterIterator will be of type NumberFormat.Field, with the attribute value being the same as the attribute key.
public Number parse(String text, ParsePosition pos)
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
most economical
subclass
returned depends on
that can represent
the
value of
isParseBigDecimal()
as well as on
number given by
the string
being parsed.
Currently, the only classes that parse returns are Long and Double, but callers should not rely on this.
Callers may use the Number methods doubleValue, longValue, etc., to obtain the type they want.
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 DecimalFormatSymbols getDecimalFormatSymbols()
public void setDecimalFormatSymbols(DecimalFormatSymbols newSymbols)
public String getPositivePrefix()
Examples: +123, $123, sFr123
public void setPositivePrefix(String newValue)
Examples: +123, $123, sFr123
public String getNegativePrefix()
Examples: -123, ($123) (with negative suffix), sFr-123
public void setNegativePrefix(String newValue)
Examples: -123, ($123) (with negative suffix), sFr-123
public String getPositiveSuffix()
Example: 123%
public void setPositiveSuffix(String newValue)
Example: 123%
public String getNegativeSuffix()
Examples: -123%, ($123) (with positive suffixes)
public void setNegativeSuffix(String newValue)
Examples: 123%
public int getMultiplier()
Examples: with 100, 1.23 -> "123", and "123" -> 1.23
public void setMultiplier(int newValue)
Examples: with 100, 1.23 -> "123", and "123" -> 1.23
public int getGroupingSize()
public void setGroupingSize(int newValue)
public boolean isDecimalSeparatorAlwaysShown()
Example: Decimal ON: 12345 -> 12345.; OFF: 12345 -> 12345
public void setDecimalSeparatorAlwaysShown(boolean newValue)
Example: Decimal ON: 12345 -> 12345.; OFF: 12345 -> 12345
public boolean isParseBigDecimal ()
public void setParseBigDecimal (boolean newValue)
public Object clone()
public boolean equals(Object obj)
public int hashCode()
public String toPattern()
public String toLocalizedPattern()
public void applyPattern(String pattern)
There is no limit to integer digits are 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 applyLocalizedPattern(String pattern)
There is no limit to integer digits are 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 setMaximumIntegerDigits(int newValue)
public void setMinimumIntegerDigits(int newValue)
public void setMaximumFractionDigits(int newValue)
public void setMinimumFractionDigits(int newValue)
public int getMaximumIntegerDigits ()
public int getMinimumIntegerDigits ()
public int getMaximumFractionDigits ()
public int getMinimumFractionDigits ()
public Currency getCurrency()
public void setCurrency(Currency currency)