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NumberFormat  |  API reference  |  Android Developers

abstract class NumberFormat : 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: 

<code>myString = NumberFormat.getInstance().format(myNumber);
  </code>

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. 

<code>NumberFormat nf = NumberFormat.getInstance();
  for (int i = 0; i &lt; myNumber.length; ++i) {
      output.println(nf.format(myNumber[i]) + "; ");
  }
  </code>

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

<code>NumberFormat nf = NumberFormat.getInstance(Locale.FRENCH);
  </code>

If the locale contains "nu" (numbers) Unicode extensions, the decimal digits, and/or the country used for formatting are overridden.

You can also use a NumberFormat to parse numbers: 

<code>myNumber = nf.parse(myString);
  </code>

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. Use getCompactNumberInstance to get the compact number format to format a number in shorter form. For example, 2000 can be formatted as "2K" in US locale. 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 or CompactNumberFormat depending on the factory method used. 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.

Summary

Nested classes
open

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

Field constant used to construct a FieldPosition object.
static Int

Field constant used to construct a FieldPosition object.
Protected constructors

Sole constructor.
Public methods
open Any

clone()

Overrides Cloneable.
open Boolean

equals(other: Any?)

Overrides equals.
String

format(number: Double)

Specialization of format.
abstract StringBuffer

format(number: Double, toAppendTo: StringBuffer, pos: FieldPosition)

Specialization of format.
open StringBuffer

format(number: Any, toAppendTo: StringBuffer, pos: FieldPosition)

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

format(number: Long)

Specialization of format.
abstract StringBuffer

format(number: Long, toAppendTo: StringBuffer, pos: FieldPosition)

Specialization of format.
open static Array<Locale!>

Returns a scientific format for the current default locale.
open Currency?

Gets the currency used by this number format when formatting currency values.
static NumberFormat

Returns a currency format for the current default FORMAT locale.
open static NumberFormat

Returns a currency format for the specified locale.
static NumberFormat

Returns a general-purpose number format for the current default FORMAT locale.
open static NumberFormat

getInstance(inLocale: Locale)

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

Returns an integer number format for the current default FORMAT locale.
open static NumberFormat

Returns an integer number format for the specified locale.
open Int

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

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

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

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

Returns a general-purpose number format for the current default FORMAT locale.
open static NumberFormat

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

Returns a percentage format for the current default FORMAT locale.
open static NumberFormat

Returns a percentage format for the specified locale.
open RoundingMode

Gets the java.math.RoundingMode used in this NumberFormat.
open Int

hashCode()

Overrides hashCode.
open Boolean

Returns true if grouping is used in this format.
open Boolean

Returns true if this format will parse numbers as integers only.
open Number?

parse(source: String)

Parses text from the beginning of the given string to produce a number.
abstract Number?

parse(source: String, 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.
Any?

Parses text from a string to produce a Number.
open Unit

setCurrency(currency: Currency)

Sets the currency used by this number format when formatting currency values.
open Unit

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

Sets the maximum number of digits allowed in the fraction portion of a number.
open Unit

Sets the maximum number of digits allowed in the integer portion of a number.
open Unit

Sets the minimum number of digits allowed in the fraction portion of a number.
open Unit

Sets the minimum number of digits allowed in the integer portion of a number.
open Unit

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

setRoundingMode(roundingMode: RoundingMode?)

Sets the java.math.RoundingMode used in this NumberFormat.
Inherited functions

From class Format

String! format(obj: Any!)

Formats an object to produce a string. This is equivalent to format(obj, new StringBuffer(), new FieldPosition(0)).toString();

AttributedCharacterIterator! formatToCharacterIterator(obj: Any!)

Formats an Object producing an AttributedCharacterIterator. You can use the returned AttributedCharacterIterator to build the resulting String, as well as to determine information about the resulting String.

Each attribute key of the AttributedCharacterIterator will be of type Field. It is up to each Format implementation to define what the legal values are for each attribute in the AttributedCharacterIterator, but typically the attribute key is also used as the attribute value.

The default implementation creates an AttributedCharacterIterator with no attributes. Subclasses that support fields should override this and create an AttributedCharacterIterator with meaningful attributes.
Any! parseObject(source: String!)

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

Constants

FRACTION_FIELD

static val FRACTION_FIELD: Int

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

Value: 1

INTEGER_FIELD

static val INTEGER_FIELD: Int

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

Value: 0

Protected constructors

NumberFormat

protected NumberFormat()

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

Public methods

clone

open fun clone(): Any

Overrides Cloneable.

Return
Any a clone of this instance.
Exceptions
java.lang.CloneNotSupportedException if the object's class does not support the Cloneable interface. Subclasses that override the clone method can also throw this exception to indicate that an instance cannot be cloned.

equals

open fun equals(other: Any?): Boolean

Overrides equals.

Parameters
obj the reference object with which to compare.
Return
Boolean true if this object is the same as the obj argument; false otherwise.

format

fun format(number: Double): String

Specialization of format.

Parameters
number Double: the double number to format
Return
String the formatted String
Exceptions
java.lang.ArithmeticException if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY

format

abstract fun format(
    number: Double, 
    toAppendTo: StringBuffer, 
    pos: FieldPosition
): StringBuffer

Specialization of format.

Parameters
number Double: the double number to format
toAppendTo StringBuffer: the StringBuffer to which the formatted text is to be appended
pos FieldPosition: keeps track on the position of the field within the returned string. For example, for formatting a number 1234567.89 in Locale.US locale, if the given fieldPosition is NumberFormat.INTEGER_FIELD, the begin index and end index of fieldPosition will be set to 0 and 9, respectively for the output string 1,234,567.89.
Return
StringBuffer the formatted StringBuffer
Exceptions
java.lang.ArithmeticException if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY

format

open fun format(
    number: Any, 
    toAppendTo: StringBuffer, 
    pos: FieldPosition
): StringBuffer

Formats a number and appends the resulting text to the given string buffer. The number can be of any subclass of java.lang.Number.

This implementation extracts the number's value using java.lang.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 java.lang.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.

Parameters
obj The object to format
toAppendTo StringBuffer: the StringBuffer to which the formatted text is to be appended
pos FieldPosition: keeps track on the position of the field within the returned string. For example, for formatting a number 1234567.89 in Locale.US locale, if the given fieldPosition is NumberFormat.INTEGER_FIELD, the begin index and end index of fieldPosition will be set to 0 and 9, respectively for the output string 1,234,567.89.
number Any: the number to format
Return
StringBuffer the value passed in as toAppendTo
Exceptions
java.lang.IllegalArgumentException if number is null or not an instance of Number.
java.lang.NullPointerException if toAppendTo or pos is null
java.lang.ArithmeticException if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY

format

fun format(number: Long): String

Specialization of format.

Parameters
number Long: the long number to format
Return
String the formatted String
Exceptions
java.lang.ArithmeticException if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY

format

abstract fun format(
    number: Long, 
    toAppendTo: StringBuffer, 
    pos: FieldPosition
): StringBuffer

Specialization of format.

Parameters
number Long: the long number to format
toAppendTo StringBuffer: the StringBuffer to which the formatted text is to be appended
pos FieldPosition: keeps track on the position of the field within the returned string. For example, for formatting a number 123456789 in Locale.US locale, if the given fieldPosition is NumberFormat.INTEGER_FIELD, the begin index and end index of fieldPosition will be set to 0 and 11, respectively for the output string 123,456,789.
Return
StringBuffer the formatted StringBuffer
Exceptions
java.lang.ArithmeticException if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY

getAvailableLocales

open static fun getAvailableLocales(): Array<Locale!>

Returns a scientific format for the current default locale. /*public* static final NumberFormat getScientificInstance() { return getInstance(Locale.getDefault(Locale.Category.FORMAT), null, SCIENTIFICSTYLE); } /** Returns a scientific format for the specified locale.

Parameters
inLocale the desired locale /*public* static NumberFormat getScientificInstance(Locale inLocale) { return getInstance(inLocale, null, SCIENTIFICSTYLE); }

getCurrency

open fun getCurrency(): Currency?

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.

Return
Currency? the currency used by this number format, or null
Exceptions
java.lang.UnsupportedOperationException if the number format class doesn't implement currency formatting

getCurrencyInstance

open static fun getCurrencyInstance(inLocale: Locale): NumberFormat

Returns a currency format for the specified locale.

If the specified locale contains the "cf" ( currency format style) Unicode extension, the returned currency format uses the style if it is available. Otherwise, the style uses the default "standard" currency format. For example, if the style designates "account", negative currency amounts use a pair of parentheses in some locales.

Parameters
inLocale Locale: the desired locale
Return
NumberFormat the NumberFormat instance for currency formatting

getInstance

static fun getInstance(): NumberFormat

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

Return
NumberFormat the NumberFormat instance for general-purpose number formatting

getInstance

open static fun getInstance(inLocale: Locale): NumberFormat

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

Parameters
inLocale Locale: the desired locale
Return
NumberFormat the NumberFormat instance for general-purpose number formatting

getIntegerInstance

open static fun getIntegerInstance(inLocale: Locale): NumberFormat

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: the desired locale
Return
NumberFormat a number format for integer values

See Also

getMaximumFractionDigits

open fun getMaximumFractionDigits(): Int

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

Return
Int the maximum number of digits.

getMaximumIntegerDigits

open fun getMaximumIntegerDigits(): Int

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

Return
Int the maximum number of digits

getMinimumFractionDigits

open fun getMinimumFractionDigits(): Int

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

Return
Int the minimum number of digits

getMinimumIntegerDigits

open fun getMinimumIntegerDigits(): Int

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

Return
Int the minimum number of digits

getNumberInstance

open static fun getNumberInstance(inLocale: Locale): NumberFormat

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

Parameters
inLocale Locale: the desired locale
Return
NumberFormat the NumberFormat instance for general-purpose number formatting

getPercentInstance

open static fun getPercentInstance(inLocale: Locale): NumberFormat

Returns a percentage format for the specified locale.

Parameters
inLocale Locale: the desired locale
Return
NumberFormat the NumberFormat instance for percentage formatting

getRoundingMode

open fun getRoundingMode(): RoundingMode

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

Return
RoundingMode The RoundingMode used for this NumberFormat.
Exceptions
java.lang.UnsupportedOperationException The default implementation always throws this exception

hashCode

open fun hashCode(): Int

Overrides hashCode.

Return
Int a hash code value for this object.

isGroupingUsed

open fun isGroupingUsed(): Boolean

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 dependent and is determined by sub-classes of NumberFormat.

Return
Boolean true if grouping is used; false otherwise

See Also

isParseIntegerOnly

open fun isParseIntegerOnly(): Boolean

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 dependent and determined by sub-classes of NumberFormat.

Return
Boolean true if numbers should be parsed as integers only; false otherwise

parse

open fun parse(source: String): Number?

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.

WARNING: Don't use this method to deserialize a number. The underlying localized number format and parsing behaviors can change across Android versions as common usage in the locale changes. Consider using the parse methods in the boxed types, e.g. Long.parseLong(String), or java.math.BigDecimal for deserializing a locale-independent decimal number.

Parameters
source String: A String whose beginning should be parsed.
Return
Number? A Number parsed from the string.
Exceptions
java.text.ParseException if the beginning of the specified string cannot be parsed.

parse

abstract fun parse(
    source: String, 
    parsePosition: ParsePosition
): Number?

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!

WARNING: Don't use this method to deserialize a number. The underlying localized number format and parsing behaviors can change across Android versions as common usage in the locale changes. Consider using the parse methods in the boxed types, e.g. Long.parseLong(String), or java.math.BigDecimal for deserializing a locale-independent decimal number.

Parameters
source String: the String to parse
parsePosition ParsePosition: the parse position
Return
Number? the parsed value

parseObject

fun parseObject(
    source: String, 
    pos: ParsePosition
): Any?

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.
Return
Any? A Number parsed from the string. In case of error, returns null.
Exceptions
java.lang.NullPointerException if source or pos is null.

setCurrency

open fun setCurrency(currency: Currency): Unit

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
Exceptions
java.lang.NullPointerException if currency is null
java.lang.UnsupportedOperationException if the number format class doesn't implement currency formatting

setGroupingUsed

open fun setGroupingUsed(newValue: Boolean): Unit

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

Parameters
newValue Boolean: true if grouping is used; false otherwise

setMaximumFractionDigits

open fun setMaximumFractionDigits(newValue: Int): Unit

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.

setMaximumIntegerDigits

open fun setMaximumIntegerDigits(newValue: Int): Unit

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.

setMinimumFractionDigits

open fun setMinimumFractionDigits(newValue: Int): Unit

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 maximumFractionDigits 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.

setMinimumIntegerDigits

open fun setMinimumIntegerDigits(newValue: Int): Unit

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.

setParseIntegerOnly

open fun setParseIntegerOnly(value: Boolean): Unit

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

Parameters
value Boolean: true if numbers should be parsed as integers only; false otherwise

setRoundingMode

open fun setRoundingMode(roundingMode: RoundingMode?): Unit

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

Parameters
roundingMode RoundingMode?: The RoundingMode to be used
Exceptions
java.lang.NullPointerException if roundingMode is null
java.lang.UnsupportedOperationException The default implementation always throws this exception

See Also