Class DecimalFormat

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

<strong>// Print out a number using the localized number, integer, currency,
// and percent format for each locale</strong>
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) {}
    }
}

Constructors

DecimalFormat

public DecimalFormat()

See Also:

NumberFormat.getInstance(), NumberFormat.getNumberInstance(), NumberFormat.getCurrencyInstance(), NumberFormat.getPercentInstance()

DecimalFormat

public DecimalFormat(String pattern)

Parameters:

pattern - a non-localized pattern string.

Throws:

NullPointerException - if pattern is null

IllegalArgumentException - if the given pattern is invalid.

See Also:

NumberFormat.getInstance(), NumberFormat.getNumberInstance(), NumberFormat.getCurrencyInstance(), NumberFormat.getPercentInstance()

DecimalFormat

public DecimalFormat(String pattern,
                     DecimalFormatSymbols symbols)

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

See Also:

NumberFormat.getInstance(), NumberFormat.getNumberInstance(), NumberFormat.getCurrencyInstance(), NumberFormat.getPercentInstance(), DecimalFormatSymbols

Methods

format

public final StringBuffer format(Object number,
                                 StringBuffer toAppendTo,
                                 FieldPosition pos)

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)

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)

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()

Returns:

the positive prefix

setPositivePrefix

public void setPositivePrefix(String newValue)

Parameters:

newValue - the new positive prefix

getNegativePrefix

public String getNegativePrefix()

Returns:

the negative prefix

setNegativePrefix

public void setNegativePrefix(String newValue)

Parameters:

newValue - the new negative prefix

getPositiveSuffix

public String getPositiveSuffix()

Returns:

the positive suffix

setPositiveSuffix

public void setPositiveSuffix(String newValue)

Parameters:

newValue - the new positive suffix

getNegativeSuffix

public String getNegativeSuffix()

Returns:

the negative suffix

setNegativeSuffix

public void setNegativeSuffix(String newValue)

Parameters:

newValue - the new negative suffix

getMultiplier

public int getMultiplier()

Gets the multiplier for use in percent, per mille, and similar formats.

Returns:

the multiplier

See Also:

setMultiplier(int)

setMultiplier

public void setMultiplier(int newValue)

Parameters:

newValue - the new multiplier

See Also:

getMultiplier()

setGroupingUsed

public void setGroupingUsed(boolean newValue)

Set whether or not grouping will be used in this format.

Overrides:

setGroupingUsed in class NumberFormat

Parameters:

newValue - true if grouping is used; false otherwise

See Also:

NumberFormat.isGroupingUsed()

getGroupingSize

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.

Returns:

the grouping size

See Also:

setGroupingSize(int), NumberFormat.isGroupingUsed(), DecimalFormatSymbols.getGroupingSeparator()

setGroupingSize

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.

Parameters:

newValue - the new grouping size

See Also:

getGroupingSize(), NumberFormat.setGroupingUsed(boolean), DecimalFormatSymbols.setGroupingSeparator(char)

isDecimalSeparatorAlwaysShown

public boolean isDecimalSeparatorAlwaysShown()

Returns:

true if the decimal separator is always shown; false otherwise

setDecimalSeparatorAlwaysShown

public void setDecimalSeparatorAlwaysShown(boolean newValue)

Parameters:

newValue - true if the decimal separator is always shown; false otherwise

isParseBigDecimal

public boolean isParseBigDecimal()

Returns whether the parse(java.lang.String, java.text.ParsePosition) method returns BigDecimal. The default value is false.

Returns:

true if the parse method returns BigDecimal; false otherwise

Since:

1.5

See Also:

setParseBigDecimal(boolean)

setParseBigDecimal

public void setParseBigDecimal(boolean newValue)

Sets whether the parse(java.lang.String, java.text.ParsePosition) method returns BigDecimal.

Parameters:

newValue - true if the parse method returns BigDecimal; false otherwise

Since:

1.5

See Also:

isParseBigDecimal()

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

hashCode

public int hashCode()

Overrides hashCode

Overrides:

hashCode in class NumberFormat

Returns:

a hash code value for this object.

See Also:

Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

toPattern

public String toPattern()

Synthesizes a pattern string that represents the current state of this Format object.

Returns:

a pattern string

See Also:

applyPattern(java.lang.String)

toLocalizedPattern

public String toLocalizedPattern()

Synthesizes a localized pattern string that represents the current state of this Format object.

Returns:

a localized pattern string

See Also:

applyPattern(java.lang.String)

applyPattern

public void applyPattern(String pattern)

Parameters:

pattern - a new pattern

Throws:

NullPointerException - if pattern is null

IllegalArgumentException - if the given pattern is invalid.

applyLocalizedPattern

public void applyLocalizedPattern(String pattern)

Parameters:

pattern - a new 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

Returns:

the maximum number of digits

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

Returns:

the minimum number of digits

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

Returns:

the maximum number of digits.

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

Returns:

the minimum number of digits

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

getRoundingMode

public RoundingMode getRoundingMode()

Gets the RoundingMode used in this DecimalFormat.

Overrides:

getRoundingMode in class NumberFormat

Returns:

The RoundingMode used for this DecimalFormat.

Since:

1.6

See Also:

setRoundingMode(RoundingMode)

setRoundingMode

public void setRoundingMode(RoundingMode roundingMode)

Sets the RoundingMode used in this DecimalFormat.

Overrides:

setRoundingMode in class NumberFormat

Parameters:

roundingMode - The RoundingMode to be used

Throws:

NullPointerException - if roundingMode is null.

Since:

1.6

See Also:

getRoundingMode()