Added in API level 24

PluralRules


open class PluralRules : Serializable
kotlin.Any
   ↳ android.icu.text.PluralRules

Defines rules for mapping non-negative numeric values onto a small set of keywords.

Rules are constructed from a text description, consisting of a series of keywords and conditions. The #select method examines each condition in order and returns the keyword for the first condition that matches the number. If none match, KEYWORD_OTHER is returned.

A PluralRules object is immutable. It contains caches for sample values, but those are synchronized.

PluralRules is Serializable so that it can be used in formatters, which are serializable.

For more information, details, and tips for writing rules, see the LDML spec, Part 3.5 Language Plural Rules

Examples:

"one: n is 1; few: n in 2..4"
  

This defines two rules, for 'one' and 'few'. The condition for 'one' is "n is 1" which means that the number must be equal to 1 for this condition to pass. The condition for 'few' is "n in 2..4" which means that the number must be between 2 and 4 inclusive - and be an integer - for this condition to pass. All other numbers are assigned the keyword "other" by the default rule.

"zero: n is 0; one: n is 1; zero: n mod 100 in 1..19"
  

This illustrates that the same keyword can be defined multiple times. Each rule is examined in order, and the first keyword whose condition passes is the one returned. Also notes that a modulus is applied to n in the last rule. Thus its condition holds for 119, 219, 319...

"one: n is 1; few: n mod 10 in 2..4 and n mod 100 not in 12..14"
  

This illustrates conjunction and negation. The condition for 'few' has two parts, both of which must be met: "n mod 10 in 2..4" and "n mod 100 not in 12..14". The first part applies a modulus to n before the test as in the previous example. The second part applies a different modulus and also uses negation, thus it matches all numbers not in 12, 13, 14, 112, 113, 114, 212, 213, 214...

Syntax:

rules         = rule (';' rule)*
  rule          = keyword ':' condition
  keyword       = <identifier>
  condition     = and_condition ('or' and_condition)*
  and_condition = relation ('and' relation)*
  relation      = not? expr not? rel not? range_list
  expr          = ('n' | 'i' | 'f' | 'v' | 't') (mod value)?
  not           = 'not' | '!'
  rel           = 'in' | 'is' | '=' | '≠' | 'within'
  mod           = 'mod' | '%'
  range_list    = (range | value) (',' range_list)*
  value         = digit+
  digit         = 0|1|2|3|4|5|6|7|8|9
  range         = value'..'value
  

Each not term inverts the meaning; however, there should not be more than one of them.

The i, f, t, and v values are defined as follows:

  • i to be the integer digits.
  • f to be the visible decimal digits, as an integer.
  • t to be the visible decimal digits—without trailing zeros—as an integer.
  • v to be the number of visible fraction digits.
  • j is defined to only match integers. That is j is 3 fails if v != 0 (eg for 3.1 or 3.0).

Examples are in the following table:

n i f v
1.0 1 0 1
1.00 1 0 2
1.3 1 3 1
1.03 1 3 2
1.23 1 23 2

An "identifier" is a sequence of characters that do not have the Unicode Pattern_Syntax or Pattern_White_Space properties.

The difference between 'in' and 'within' is that 'in' only includes integers in the specified range, while 'within' includes all values. Using 'within' with a range_list consisting entirely of values is the same as using 'in' (it's not an error).

Summary

Nested classes

Type of plurals and PluralRules.

Constants
static String

Common name for the 'paucal' or other special plural form.

static String

Common name for the arabic (11 to 99) plural form.

static String

Common name for the 'singular' plural form.

static String

Common name for the default plural form.

static String

Common name for the 'dual' plural form.

static String

Common name for the 'zero' plural form.

static Double

Value returned by getUniqueKeywordValue when there is no unique value to return.

Public methods
open static PluralRules!
createRules(description: String!)

Creates a PluralRules from a description if it is parsable, otherwise returns null.

open Boolean
equals(other: Any?)

Indicates whether some other object is "equal to" this one.

open Boolean

Returns true if rhs is equal to this.

open static PluralRules!
forLocale(locale: ULocale!)

Provides access to the predefined cardinal-number PluralRules for a given locale.

open static PluralRules!
forLocale(locale: Locale!)

Provides access to the predefined cardinal-number PluralRules for a given java.util.Locale.

open static PluralRules!

Provides access to the predefined PluralRules for a given locale and the plural type.

open static PluralRules!

Provides access to the predefined PluralRules for a given java.util.Locale and the plural type.

open MutableCollection<Double!>!

Returns all the values that trigger this keyword, or null if the number of such values is unlimited.

open MutableSet<String!>!

Returns a set of all rule keywords used in this PluralRules object.

open MutableCollection<Double!>!
getSamples(keyword: String!)

Returns a list of integer values for which select() would return that keyword, or null if the keyword is not defined.

open Double

Returns the unique value that this keyword matches, or NO_UNIQUE_VALUE if the keyword matches multiple values or is not defined for this PluralRules.

open static PluralRules!
parseDescription(description: String!)

Parses a plural rules description and returns a PluralRules.

open String!
select(number: Double)

Given a floating-point number, returns the keyword of the first rule that applies to the number.

open String!

Given a formatted number, returns the keyword of the first rule that applies to the number.

open String!

Given a formatted number range, returns the overall plural form of the range.

open String

Returns a string representation of the object.

Properties
static PluralRules!

The default rules that accept any number and return KEYWORD_OTHER.

Constants

KEYWORD_FEW

Added in API level 24
static val KEYWORD_FEW: String

Common name for the 'paucal' or other special plural form.

Value: "few"

KEYWORD_MANY

Added in API level 24
static val KEYWORD_MANY: String

Common name for the arabic (11 to 99) plural form.

Value: "many"

KEYWORD_ONE

Added in API level 24
static val KEYWORD_ONE: String

Common name for the 'singular' plural form.

Value: "one"

KEYWORD_OTHER

Added in API level 24
static val KEYWORD_OTHER: String

Common name for the default plural form. This name is returned for values to which no other form in the rule applies. It can additionally be assigned rules of its own.

Value: "other"

KEYWORD_TWO

Added in API level 24
static val KEYWORD_TWO: String

Common name for the 'dual' plural form.

Value: "two"

KEYWORD_ZERO

Added in API level 24
static val KEYWORD_ZERO: String

Common name for the 'zero' plural form.

Value: "zero"

NO_UNIQUE_VALUE

Added in API level 24
static val NO_UNIQUE_VALUE: Double

Value returned by getUniqueKeywordValue when there is no unique value to return.

Value: -0.00123456777

Public methods

createRules

Added in API level 24
open static fun createRules(description: String!): PluralRules!

Creates a PluralRules from a description if it is parsable, otherwise returns null.

Parameters
description String!: the rule description.
Return
PluralRules! the PluralRules

equals

Added in API level 24
open fun equals(other: Any?): Boolean

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

  • It is reflexive: for any non-null reference value x, x.equals(x) should return true.
  • It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
  • It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
  • It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
  • For any non-null reference value x, x.equals(null) should return false.

An equivalence relation partitions the elements it operates on into equivalence classes; all the members of an equivalence class are equal to each other. Members of an equivalence class are substitutable for each other, at least for some purposes.

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

equals

Added in API level 24
open fun equals(rhs: PluralRules!): Boolean

Returns true if rhs is equal to this.

Parameters
rhs PluralRules!: the PluralRules to compare to.
Return
Boolean true if this and rhs are equal.

forLocale

Added in API level 24
open static fun forLocale(locale: ULocale!): PluralRules!

Provides access to the predefined cardinal-number PluralRules for a given locale. Same as forLocale(locale, PluralType.CARDINAL).

ICU defines plural rules for many locales based on CLDR Language Plural Rules. For these predefined rules, see CLDR page at https://unicode-org.github.io/cldr-staging/charts/latest/supplemental/language_plural_rules.html

Parameters
locale ULocale!: The locale for which a PluralRules object is returned.
Return
PluralRules! The predefined PluralRules object for this locale. If there's no predefined rules for this locale, the rules for the closest parent in the locale hierarchy that has one will be returned. The final fallback always returns the default rules.

forLocale

Added in API level 24
open static fun forLocale(locale: Locale!): PluralRules!

Provides access to the predefined cardinal-number PluralRules for a given java.util.Locale. Same as forLocale(locale, PluralType.CARDINAL).

ICU defines plural rules for many locales based on CLDR Language Plural Rules. For these predefined rules, see CLDR page at https://unicode-org.github.io/cldr-staging/charts/latest/supplemental/language_plural_rules.html

Parameters
locale Locale!: The locale for which a PluralRules object is returned.
Return
PluralRules! The predefined PluralRules object for this locale. If there's no predefined rules for this locale, the rules for the closest parent in the locale hierarchy that has one will be returned. The final fallback always returns the default rules.

forLocale

Added in API level 24
open static fun forLocale(
    locale: ULocale!,
    type: PluralRules.PluralType!
): PluralRules!

Provides access to the predefined PluralRules for a given locale and the plural type.

ICU defines plural rules for many locales based on CLDR Language Plural Rules. For these predefined rules, see CLDR page at https://unicode-org.github.io/cldr-staging/charts/latest/supplemental/language_plural_rules.html

Parameters
locale ULocale!: The locale for which a PluralRules object is returned.
type PluralRules.PluralType!: The plural type (e.g., cardinal or ordinal).
Return
PluralRules! The predefined PluralRules object for this locale. If there's no predefined rules for this locale, the rules for the closest parent in the locale hierarchy that has one will be returned. The final fallback always returns the default rules.

forLocale

Added in API level 24
open static fun forLocale(
    locale: Locale!,
    type: PluralRules.PluralType!
): PluralRules!

Provides access to the predefined PluralRules for a given java.util.Locale and the plural type.

ICU defines plural rules for many locales based on CLDR Language Plural Rules. For these predefined rules, see CLDR page at https://unicode-org.github.io/cldr-staging/charts/latest/supplemental/language_plural_rules.html

Parameters
locale Locale!: The locale for which a PluralRules object is returned.
type PluralRules.PluralType!: The plural type (e.g., cardinal or ordinal).
Return
PluralRules! The predefined PluralRules object for this locale. If there's no predefined rules for this locale, the rules for the closest parent in the locale hierarchy that has one will be returned. The final fallback always returns the default rules.

getAllKeywordValues

Added in API level 24
open fun getAllKeywordValues(keyword: String!): MutableCollection<Double!>!

Returns all the values that trigger this keyword, or null if the number of such values is unlimited.

Parameters
keyword String!: the keyword
Return
MutableCollection<Double!>! the values that trigger this keyword, or null. The returned collection is immutable. It will be empty if the keyword is not defined.

getKeywords

Added in API level 24
open fun getKeywords(): MutableSet<String!>!

Returns a set of all rule keywords used in this PluralRules object. The rule "other" is always present by default.

Return
MutableSet<String!>! The set of keywords.

getSamples

Added in API level 24
open fun getSamples(keyword: String!): MutableCollection<Double!>!

Returns a list of integer values for which select() would return that keyword, or null if the keyword is not defined. The returned collection is unmodifiable. The returned list is not complete, and there might be additional values that would return the keyword.

Parameters
keyword String!: the keyword to test
Return
MutableCollection<Double!>! a list of values matching the keyword.

getUniqueKeywordValue

Added in API level 24
open fun getUniqueKeywordValue(keyword: String!): Double

Returns the unique value that this keyword matches, or NO_UNIQUE_VALUE if the keyword matches multiple values or is not defined for this PluralRules.

Parameters
keyword String!: the keyword to check for a unique value
Return
Double The unique value for the keyword, or NO_UNIQUE_VALUE.

parseDescription

Added in API level 24
open static fun parseDescription(description: String!): PluralRules!

Parses a plural rules description and returns a PluralRules.

Parameters
description String!: the rule description.
Exceptions
java.text.ParseException if the description cannot be parsed. The exception index is typically not set, it will be -1.

select

Added in API level 24
open fun select(number: Double): String!

Given a floating-point number, returns the keyword of the first rule that applies to the number.

Parameters
number Double: The number for which the rule has to be determined.
Return
String! The keyword of the selected rule.

select

Added in API level 31
open fun select(number: FormattedNumber!): String!

Given a formatted number, returns the keyword of the first rule that applies to the number. A FormattedNumber allows you to specify an exponent or trailing zeros, which can affect the plural category. To get a FormattedNumber, see NumberFormatter.

Parameters
number FormattedNumber!: The number for which the rule has to be determined.
Return
String! The keyword of the selected rule.

select

Added in API level 33
open fun select(range: FormattedNumberRange!): String!

Given a formatted number range, returns the overall plural form of the range. For example, "3-5" returns "other" in English. To get a FormattedNumberRange, see android.icu.number.NumberRangeFormatter. This method only works if PluralRules was created with a locale. If it was created from PluralRules.createRules(), or if it was deserialized, this method throws UnsupportedOperationException.

Parameters
range FormattedNumberRange!: The number range onto which the rules will be applied.
Return
String! The keyword of the selected rule.
Exceptions
java.lang.UnsupportedOperationException If called on an instance without plural ranges data.

toString

Added in API level 24
open fun toString(): String

Returns a string representation of the object.

Return
String a string representation of the object.

Properties

DEFAULT

Added in API level 24
static val DEFAULT: PluralRules!

The default rules that accept any number and return KEYWORD_OTHER.