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NumberFormat

public abstract class NumberFormat
extends Format

java.lang.Object
   ↳ java.text.Format
     ↳ java.text.NumberFormat
Known Direct Subclasses


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 < myNumber.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:

Summary

Nested classes

class NumberFormat.Field

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

Constants

int FRACTION_FIELD

Field constant used to construct a FieldPosition object.

int INTEGER_FIELD

Field constant used to construct a FieldPosition object.

Protected constructors

NumberFormat()

Sole constructor.

Public methods

Object clone()

Overrides Cloneable

boolean equals(Object obj)

Overrides equals

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

Formats a number and appends the resulting text to the given string buffer.

final String format(double number)

Specialization of format.

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

Specialization of format.

final String format(long number)

Specialization of format.

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

Specialization of format.

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(Locale inLocale)

Returns a currency format for the specified locale.

static final NumberFormat getCurrencyInstance()

Returns a currency format for the current default locale.

static final 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 final 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 final 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(Locale inLocale)

Returns a percentage format for the specified locale.

static final NumberFormat getPercentInstance()

Returns a percentage format for the current default locale.

RoundingMode getRoundingMode()

Gets the RoundingMode used in this NumberFormat.

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.

final 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.

void setRoundingMode(RoundingMode roundingMode)

Sets the RoundingMode used in this NumberFormat.

Inherited methods

From class java.text.Format
From class java.lang.Object

Constants

FRACTION_FIELD

Added in API level 1
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:

Constant Value: 1 (0x00000001)

INTEGER_FIELD

Added in API level 1
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:

Constant Value: 0 (0x00000000)

Protected constructors

NumberFormat

Added in API level 1
NumberFormat ()

Sole constructor. (For invocation by subclass constructors, typically implicit.)

Public methods

clone

Added in API level 1
Object clone ()

Overrides Cloneable

Returns
Object a clone of this instance.

equals

Added in API level 1
boolean equals (Object obj)

Overrides equals

Parameters
obj Object: the reference object with which to compare.
Returns
boolean true if this object is the same as the obj argument; false otherwise.

format

Added in API level 1
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 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 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.

Parameters
number Object: the number to format
toAppendTo StringBuffer: the StringBuffer to which the formatted text is to be appended
pos FieldPosition: On input: an alignment field, if desired. On output: the offsets of the alignment field.
Returns
StringBuffer 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:

format

Added in API level 1
String format (double number)

Specialization of format.

Parameters
number double
Returns
String
Throws
ArithmeticException if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY

See also:

format

Added in API level 1
StringBuffer format (double number, 
                StringBuffer toAppendTo, 
                FieldPosition pos)

Specialization of format.

Parameters
number double
toAppendTo StringBuffer
pos FieldPosition
Returns
StringBuffer
Throws
ArithmeticException if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY

See also:

format

Added in API level 1
String format (long number)

Specialization of format.

Parameters
number long
Returns
String
Throws
ArithmeticException if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY

See also:

format

Added in API level 1
StringBuffer format (long number, 
                StringBuffer toAppendTo, 
                FieldPosition pos)

Specialization of format.

Parameters
number long
toAppendTo StringBuffer
pos FieldPosition
Returns
StringBuffer
Throws
ArithmeticException if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY

See also:

getAvailableLocales

Added in API level 1
Locale[] getAvailableLocales ()

Returns an array of all locales for which the get*Instance methods of this class can return localized instances. The returned array represents the union of locales supported by the Java runtime and by installed NumberFormatProvider implementations. It must contain at least a Locale instance equal to Locale.US.

Returns
Locale[] An array of locales for which localized NumberFormat instances are available.

getCurrency

Added in API level 1
Currency getCurrency ()

Gets the currency used by this number format when formatting currency values. The initial value is derived in a locale dependent way. The returned value may be null if no valid currency could be determined and no currency has been set using setCurrency.

The default implementation throws UnsupportedOperationException.

Returns
Currency the currency used by this number format, or null
Throws
UnsupportedOperationException if the number format class doesn't implement currency formatting

getCurrencyInstance

Added in API level 1
NumberFormat getCurrencyInstance (Locale inLocale)

Returns a currency format for the specified locale.

Parameters
inLocale Locale
Returns
NumberFormat

getCurrencyInstance

Added in API level 1
NumberFormat getCurrencyInstance ()

Returns a currency format for the current default locale.

Returns
NumberFormat

getInstance

Added in API level 1
NumberFormat getInstance ()

Returns a general-purpose number format for the current default locale. This is the same as calling getNumberInstance().

Returns
NumberFormat

getInstance

Added in API level 1
NumberFormat getInstance (Locale inLocale)

Returns a general-purpose number format for the specified locale. This is the same as calling getNumberInstance(inLocale).

Parameters
inLocale Locale
Returns
NumberFormat

getIntegerInstance

Added in API level 1
NumberFormat getIntegerInstance ()

Returns an integer number format for the current default locale. The returned number format is configured to round floating point numbers to the nearest integer using half-even rounding (see RoundingMode.HALF_EVEN) for formatting, and to parse only the integer part of an input string (see isParseIntegerOnly).

Returns
NumberFormat a number format for integer values

See also:

getIntegerInstance

Added in API level 1
NumberFormat getIntegerInstance (Locale inLocale)

Returns an integer number format for the specified locale. The returned number format is configured to round floating point numbers to the nearest integer using half-even rounding (see RoundingMode.HALF_EVEN) for formatting, and to parse only the integer part of an input string (see isParseIntegerOnly).

Parameters
inLocale Locale
Returns
NumberFormat a number format for integer values

See also:

getMaximumFractionDigits

Added in API level 1
int getMaximumFractionDigits ()

Returns the maximum number of digits allowed in the fraction portion of a number.

Returns
int

See also:

getMaximumIntegerDigits

Added in API level 1
int getMaximumIntegerDigits ()

Returns the maximum number of digits allowed in the integer portion of a number.

Returns
int

See also:

getMinimumFractionDigits

Added in API level 1
int getMinimumFractionDigits ()

Returns the minimum number of digits allowed in the fraction portion of a number.

Returns
int

See also:

getMinimumIntegerDigits

Added in API level 1
int getMinimumIntegerDigits ()

Returns the minimum number of digits allowed in the integer portion of a number.

Returns
int

See also:

getNumberInstance

Added in API level 1
NumberFormat getNumberInstance ()

Returns a general-purpose number format for the current default locale.

Returns
NumberFormat

getNumberInstance

Added in API level 1
NumberFormat getNumberInstance (Locale inLocale)

Returns a general-purpose number format for the specified locale.

Parameters
inLocale Locale
Returns
NumberFormat

getPercentInstance

Added in API level 1
NumberFormat getPercentInstance (Locale inLocale)

Returns a percentage format for the specified locale.

Parameters
inLocale Locale
Returns
NumberFormat

getPercentInstance

Added in API level 1
NumberFormat getPercentInstance ()

Returns a percentage format for the current default locale.

Returns
NumberFormat

getRoundingMode

Added in API level 9
RoundingMode getRoundingMode ()

Gets the RoundingMode used in this NumberFormat. The default implementation of this method in NumberFormat always throws UnsupportedOperationException. Subclasses which handle different rounding modes should override this method.

Returns
RoundingMode The RoundingMode used for this NumberFormat.
Throws
UnsupportedOperationException The default implementation always throws this exception

See also:

hashCode

Added in API level 1
int hashCode ()

Overrides hashCode

Returns
int a hash code value for this object.

isGroupingUsed

Added in API level 1
boolean isGroupingUsed ()

Returns true if grouping is used in this format. For example, in the English locale, with grouping on, the number 1234567 might be formatted as "1,234,567". The grouping separator as well as the size of each group is locale dependant and is determined by sub-classes of NumberFormat.

Returns
boolean

See also:

isParseIntegerOnly

Added in API level 1
boolean isParseIntegerOnly ()

Returns true if this format will parse numbers as integers only. For example in the English locale, with ParseIntegerOnly true, the string "1234." would be parsed as the integer value 1234 and parsing would stop at the "." character. Of course, the exact format accepted by the parse operation is locale dependant and determined by sub-classes of NumberFormat.

Returns
boolean

parse

Added in API level 1
Number parse (String source)

Parses text from the beginning of the given string to produce a number. The method may not use the entire text of the given string.

See the parse(String, ParsePosition) method for more information on number parsing.

Parameters
source String: A String whose beginning should be parsed.
Returns
Number A Number parsed from the string.
Throws
ParseException if the beginning of the specified string cannot be parsed.

parse

Added in API level 1
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!

Parameters
source String
parsePosition ParsePosition
Returns
Number

See also:

parseObject

Added in API level 1
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.

Parameters
source String: A String, part of which should be parsed.
pos ParsePosition: A ParsePosition object with index and error index information as described above.
Returns
Object A Number parsed from the string. In case of error, returns null.
Throws
NullPointerException if pos is null.

setCurrency

Added in API level 1
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 default implementation throws UnsupportedOperationException.

Parameters
currency Currency: the new currency to be used by this number format
Throws
UnsupportedOperationException if the number format class doesn't implement currency formatting
NullPointerException if currency is null

setGroupingUsed

Added in API level 1
void setGroupingUsed (boolean newValue)

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

Parameters
newValue boolean

See also:

setMaximumFractionDigits

Added in API level 1
void setMaximumFractionDigits (int newValue)

Sets the maximum number of digits allowed in the fraction portion of a number. maximumFractionDigits must be >= minimumFractionDigits. If the new value for maximumFractionDigits is less than the current value of minimumFractionDigits, then minimumFractionDigits will also be set to the new value.

Parameters
newValue int: 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:

setMaximumIntegerDigits

Added in API level 1
void setMaximumIntegerDigits (int newValue)

Sets the maximum number of digits allowed in the integer portion of a number. maximumIntegerDigits must be >= minimumIntegerDigits. If the new value for maximumIntegerDigits is less than the current value of minimumIntegerDigits, then minimumIntegerDigits will also be set to the new value.

Parameters
newValue int: 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:

setMinimumFractionDigits

Added in API level 1
void setMinimumFractionDigits (int newValue)

Sets the minimum number of digits allowed in the fraction portion of a number. minimumFractionDigits must be <= maximumFractionDigits. If the new value for minimumFractionDigits exceeds the current value of maximumFractionDigits, then maximumIntegerDigits will also be set to the new value

Parameters
newValue int: 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:

setMinimumIntegerDigits

Added in API level 1
void setMinimumIntegerDigits (int newValue)

Sets the minimum number of digits allowed in the integer portion of a number. minimumIntegerDigits must be <= maximumIntegerDigits. If the new value for minimumIntegerDigits exceeds the current value of maximumIntegerDigits, then maximumIntegerDigits will also be set to the new value

Parameters
newValue int: 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:

setParseIntegerOnly

Added in API level 1
void setParseIntegerOnly (boolean value)

Sets whether or not numbers should be parsed as integers only.

Parameters
value boolean

See also:

setRoundingMode

Added in API level 9
void setRoundingMode (RoundingMode roundingMode)

Sets the RoundingMode used in this NumberFormat. The default implementation of this method in NumberFormat always throws UnsupportedOperationException. Subclasses which handle different rounding modes should override this method.

Parameters
roundingMode RoundingMode: The RoundingMode to be used
Throws
UnsupportedOperationException The default implementation always throws this exception
NullPointerException if roundingMode is null

See also:

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