Number format object java

Class 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)

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 ResourceBundle s.

Patterns

Pattern: PositivePattern PositivePattern ; NegativePattern PositivePattern: Prefixopt Number Suffixopt NegativePattern: Prefixopt Number Suffixopt Prefix: any Unicode characters except U+FFFE, U+FFFF, and special characters Suffix: any Unicode characters except U+FFFE, U+FFFF, 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 minus sign ( ‘-‘ U+002D HYPHEN-MINUS ) 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, grouping 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 grouping 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.

Chart showing symbol, location, localized, and meaning.

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 or monetary 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
U+2030	Prefix or suffix	Yes	Multiply by 1000 and show as per mille value
¤ ( U+00A4 )	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/grouping separators are used instead of the decimal/grouping separators.
‘	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

• 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» .

  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 U+FFFD . 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 U+221E , with the positive or negative prefixes and suffixes applied. The infinity string is determined by the DecimalFormatSymbols object.

  • 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) <> > > 

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  Number format object java

  NumberFormat is the abstract base class for all number formats. This class provides the interface for formatting and parsing numbers. NumberFormat also provides methods for determining which locales have number formats, and what their names are. NumberFormat helps you to format and parse numbers for any locale. Your code can be completely independent of the locale conventions for decimal points, thousands-separators, or even the particular decimal digits used, or whether the number format is even decimal. To format a number for the current Locale, use one of the factory class methods:

   myString = NumberFormat.getInstance().format(myNumber); 

  If you are formatting multiple numbers, it is more efficient to get the format and use it multiple times so that the system doesn’t have to fetch the information about the local language and country conventions multiple times.

   NumberFormat nf = NumberFormat.getInstance(); for (int i = 0; i

   NumberFormat nf = NumberFormat.getInstance(Locale.FRENCH); 

   myNumber = nf.parse(myString); 

  • progressively parse through pieces of a string
  • align the decimal point and other areas
  1. If you are using a monospaced font with spacing for alignment, you can pass the FieldPosition in your format call, with field = INTEGER_FIELD . On output, getEndIndex will be set to the offset between the last character of the integer and the decimal. Add (desiredSpaceCount — getEndIndex) spaces at the front of the string.
  2. If you are using proportional fonts, instead of padding with spaces, measure the width of the string in pixels from the start to getEndIndex . Then move the pen by (desiredPixelWidth — widthToAlignmentPoint) before drawing the text. It also works where there is no decimal, but possibly additional characters at the end, e.g., with parentheses in negative numbers: «(12)» for -12.

  Synchronization

  Number 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.

  Nested Class Summary

  Defines constants that are used as attribute keys in the AttributedCharacterIterator returned from NumberFormat.formatToCharacterIterator and as field identifiers in FieldPosition .

  Field Summary

  Constructor Summary

  Method Summary

  Returns an array of all locales for which the get*Instance methods of this class can return localized instances.

  Returns a Long if possible (e.g., within the range [Long.MIN_VALUE, Long.MAX_VALUE] and with no decimals), otherwise a Double.

  Methods inherited from class java.text.Format

  Methods inherited from class java.lang.Object

  Field Detail

  INTEGER_FIELD

  public static final int INTEGER_FIELD

  Field constant used to construct a FieldPosition object. Signifies that the position of the integer part of a formatted number should be returned.

  FRACTION_FIELD

  public static final int FRACTION_FIELD

  Field constant used to construct a FieldPosition object. Signifies that the position of the fraction part of a formatted number should be returned.

  Constructor Detail

  NumberFormat

  Method Detail

  format

  public 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 extracts the number’s value using Number.longValue() for all integral type values that can be converted to long without loss of information, including BigInteger values with a bit length of less than 64, and Number.doubleValue() for all other types. It then calls format(long,java.lang.StringBuffer,java.text.FieldPosition) or format(double,java.lang.StringBuffer,java.text.FieldPosition) . This may result in loss of magnitude information and precision for BigInteger and BigDecimal values.

  parseObject

  public final Object parseObject(String source, 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. See the parse(String, ParsePosition) method for more information on number parsing.

  format

  format

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