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NumberFormatter

public final class NumberFormatter
extends Object

java.lang.Object
   ↳ android.icu.number.NumberFormatter


The main entrypoint to the localized number formatting library introduced in ICU 60. Basic usage examples:

 // Most basic usage:
 NumberFormatter.withLocale(...).format(123).toString();  // 1,234 in en-US

 // Custom notation, unit, and rounding strategy:
 NumberFormatter.with()
     .notation(Notation.compactShort())
     .unit(Currency.getInstance("EUR"))
     .precision(Precision.maxDigits(2))
     .locale(...)
     .format(1234)
     .toString();  // €1.2K in en-US

 // Create a formatter in a private static final field:
 private static final LocalizedNumberFormatter formatter = NumberFormatter.withLocale(...)
     .unit(NoUnit.PERCENT)
     .precision(Precision.fixedFraction(3));
 formatter.format(5.9831).toString();  // 5.983% in en-US

 // Create a "template" in a private static final field but without setting a locale until the call site:
 private static final UnlocalizedNumberFormatter template = NumberFormatter.with()
     .sign(SignDisplay.ALWAYS)
     .unitWidth(UnitWidth.FULL_NAME);
 template.locale(...).format(new Measure(1234, MeasureUnit.METER)).toString();  // +1,234 meters in en-US
 

This API offers more features than DecimalFormat and is geared toward new users of ICU.

NumberFormatter instances (i.e., LocalizedNumberFormatter and UnlocalizedNumberFormatter) are immutable and thread safe. This means that invoking a configuration method has no effect on the receiving instance; you must store and use the new number formatter instance it returns instead.

 UnlocalizedNumberFormatter formatter = UnlocalizedNumberFormatter.with()
         .notation(Notation.scientific());
 formatter.precision(Precision.maxFraction(2)); // does nothing!
 formatter.locale(ULocale.ENGLISH).format(9.8765).toString(); // prints "9.8765E0", not "9.88E0"
 

This API is based on the fluent design pattern popularized by libraries such as Google's Guava. For extensive details on the design of this API, read the design doc.

Summary

Nested classes

enum NumberFormatter.DecimalSeparatorDisplay

An enum declaring how to render the decimal separator. 

enum NumberFormatter.GroupingStrategy

An enum declaring the strategy for when and how to display grouping separators (i.e., the separator, often a comma or period, after every 2-3 powers of ten). 

enum NumberFormatter.SignDisplay

An enum declaring how to denote positive and negative numbers. 

enum NumberFormatter.UnitWidth

An enum declaring how to render units, including currencies. 

Public methods

static UnlocalizedNumberFormatter with()

Call this method at the beginning of a NumberFormatter fluent chain in which the locale is not currently known at the call site.

static LocalizedNumberFormatter withLocale(Locale locale)

Call this method at the beginning of a NumberFormatter fluent chain in which the locale is known at the call site.

static LocalizedNumberFormatter withLocale(ULocale locale)

Call this method at the beginning of a NumberFormatter fluent chain in which the locale is known at the call site.

Inherited methods

Public methods

with

public static UnlocalizedNumberFormatter with ()

Call this method at the beginning of a NumberFormatter fluent chain in which the locale is not currently known at the call site.

Returns
UnlocalizedNumberFormatter An UnlocalizedNumberFormatter, to be used for chaining.

withLocale

public static LocalizedNumberFormatter withLocale (Locale locale)

Call this method at the beginning of a NumberFormatter fluent chain in which the locale is known at the call site.

Parameters
locale Locale: The locale from which to load formats and symbols for number formatting.

Returns
LocalizedNumberFormatter A LocalizedNumberFormatter, to be used for chaining.

withLocale

public static LocalizedNumberFormatter withLocale (ULocale locale)

Call this method at the beginning of a NumberFormatter fluent chain in which the locale is known at the call site.

Parameters
locale ULocale: The locale from which to load formats and symbols for number formatting.

Returns
LocalizedNumberFormatter A LocalizedNumberFormatter, to be used for chaining.