java.text
Class NumberFormat

java.lang.Object   
  java.text.Format   
      java.text.NumberFormat

All Implemented Interfaces:

Serializable , Cloneable

Direct Known Subclasses:

ChoiceFormat , DecimalFormat

public abstract class NumberFormat
extends Format   

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 < a.length; ++i) {
     output.println(nf.format(myNumber[i]) + "; ");
 }
 

To format a number for a different Locale, specify it in the call to getInstance.

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

You can also use a NumberFormat to parse numbers:

 myNumber = nf.parse(myString);
 

Use getInstance or getNumberInstance to get the normal number format. Use getIntegerInstance to get an integer number format. Use getCurrencyInstance to get the currency number format. And use getPercentInstance to get a format for displaying percentages. With this format, a fraction like 0.53 is displayed as 53%.

You can also control the display of numbers with such methods as setMinimumFractionDigits. If you want even more control over the format or parsing, or want to give your users more control, you can try casting the NumberFormat you get from the factory methods to a DecimalFormat. This will work for the vast majority of locales; just remember to put it in a try block in case you encounter an unusual one.

NumberFormat and DecimalFormat are designed such that some controls work for formatting and others work for parsing. The following is the detailed description for each these control methods,

setParseIntegerOnly : only affects parsing, e.g. if true, "3456.78" -> 3456 (and leaves the parse position just after index 6) if false, "3456.78" -> 3456.78 (and leaves the parse position just after index 8) This is independent of formatting. If you want to not show a decimal point where there might be no digits after the decimal point, use setDecimalSeparatorAlwaysShown.

setDecimalSeparatorAlwaysShown : only affects formatting, and only where there might be no digits after the decimal point, such as with a pattern like "#,##0.##", e.g., if true, 3456.00 -> "3,456." if false, 3456.00 -> "3456" This is independent of parsing. If you want parsing to stop at the decimal point, use setParseIntegerOnly.

You can also use forms of the parse and format methods with ParsePosition and FieldPosition to allow you to:

• progressively parse through pieces of a string
• align the decimal point and other areas

For example, you can align numbers in two ways:

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.

See Also:

DecimalFormat , ChoiceFormat , Serialized Form

Nested Class Summary

static class

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

Field Summary

static int	FRACTION_FIELD Field constant used to construct a FieldPosition object.
static int	INTEGER_FIELD Field constant used to construct a FieldPosition object.

Constructor Summary

NumberFormat ()

Method Summary

Object	clone () Overrides Cloneable
boolean	equals (Object obj) Overrides equals
String	format (double number) Specialization of format.
abstract StringBuffer	format (double number, StringBuffer toAppendTo, FieldPosition pos) Specialization of format.
String	format (long number) Specialization of format.
abstract StringBuffer	format (long number, StringBuffer toAppendTo, FieldPosition pos) Specialization of format.
StringBuffer	format (Object number, StringBuffer toAppendTo, FieldPosition pos) Formats a number and appends the resulting text to the given string buffer.
static Locale []	getAvailableLocales () Returns an array of all locales for which the get*Instance methods of this class can return localized instances.
Currency	getCurrency () Gets the currency used by this number format when formatting currency values.
static NumberFormat	getCurrencyInstance () Returns a currency format for the current default locale.
static NumberFormat	getCurrencyInstance (Locale inLocale) Returns a currency format for the specified locale.
static NumberFormat	getInstance () Returns a general-purpose number format for the current default locale.
static NumberFormat	getInstance (Locale inLocale) Returns a general-purpose number format for the specified locale.
static NumberFormat	getIntegerInstance () Returns an integer number format for the current default locale.
static NumberFormat	getIntegerInstance (Locale inLocale) Returns an integer number format for the specified locale.
int	getMaximumFractionDigits () Returns the maximum number of digits allowed in the fraction portion of a number.
int	getMaximumIntegerDigits () Returns the maximum number of digits allowed in the integer portion of a number.
int	getMinimumFractionDigits () Returns the minimum number of digits allowed in the fraction portion of a number.
int	getMinimumIntegerDigits () Returns the minimum number of digits allowed in the integer portion of a number.
static NumberFormat	getNumberInstance () Returns a general-purpose number format for the current default locale.
static NumberFormat	getNumberInstance (Locale inLocale) Returns a general-purpose number format for the specified locale.
static NumberFormat	getPercentInstance () Returns a percentage format for the current default locale.
static NumberFormat	getPercentInstance (Locale inLocale) Returns a percentage format for the specified locale.
int	hashCode () Overrides hashCode
boolean	isGroupingUsed () Returns true if grouping is used in this format.
boolean	isParseIntegerOnly () Returns true if this format will parse numbers as integers only.
Number	parse (String source) Parses text from the beginning of the given string to produce a number.
abstract Number	parse (String source, ParsePosition parsePosition) Returns a Long if possible (e.g., within the range [Long.MIN_VALUE, Long.MAX_VALUE] and with no decimals), otherwise a Double.
Object	parseObject (String source, 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	setGroupingUsed (boolean newValue) Set whether or not grouping will be used in this format.
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	setParseIntegerOnly (boolean value) Sets whether or not numbers should be parsed as integers only.

Methods inherited from class java.text.Format

format , formatToCharacterIterator , parseObject

Methods inherited from class java.lang.Object

finalize , getClass , notify , notifyAll , toString , wait , wait , wait

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.

See Also:

FieldPosition , Constant Field Values

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.

See Also:

FieldPosition , Constant Field Values

Constructor Detail

NumberFormat

public 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.

Specified by:

format in class Format

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

See Also:

FieldPosition

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.

Specified by:

parseObject in class Format

Parameters:

source - A String, part of which should be parsed.

pos - A ParsePosition object with index and error index information as described above.

Returns:

A Number parsed from the string. In case of error, returns null.

Throws:

NullPointerException - if pos is null.

format

public final String    format(double number)

Specialization of format.

See Also:

Format.format(java.lang.Object)

format

public final String    format(long number)

Specialization of format.

See Also:

Format.format(java.lang.Object)

format

public abstract StringBuffer    format(double number,
                                    StringBuffer    toAppendTo,
                                    FieldPosition    pos)

Specialization of format.

See Also:

Format.format(java.lang.Object)

format

public abstract StringBuffer    format(long number,
                                    StringBuffer    toAppendTo,
                                    FieldPosition    pos)

Specialization of format.

See Also:

Format.format(java.lang.Object)

parse

public abstract Number    parse(String    source,
                             ParsePosition    parsePosition)

Returns a Long if possible (e.g., within the range [Long.MIN_VALUE, Long.MAX_VALUE] and with no decimals), otherwise a Double. If IntegerOnly is set, will stop at a decimal point (or equivalent; e.g., for rational numbers "1 2/3", will stop after the 1). Does not throw an exception; if no object can be parsed, index is unchanged!

See Also:

isParseIntegerOnly() , Format.parseObject(java.lang.String, java.text.ParsePosition)

parse

public Number    parse(String    source)
             throws ParseException   

Parse