Added in API level 24

Summary: Constants | Fields | Methods | Inherited Methods

PluralRules

Kotlin |Java

public class PluralRules
extends Object implements Serializable

java.lang.Object
↳	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(FormattedNumber) 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' | '=' | '\u2260' | '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\u2014without trailing zeros\u2014as 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

Constants
`String`	`KEYWORD_FEW` Common name for the 'paucal' or other special plural form.
`String`	`KEYWORD_MANY` Common name for the arabic (11 to 99) plural form.
`String`	`KEYWORD_ONE` Common name for the 'singular' plural form.
`String`	`KEYWORD_OTHER` Common name for the default plural form.
`String`	`KEYWORD_TWO` Common name for the 'dual' plural form.
`String`	`KEYWORD_ZERO` Common name for the 'zero' plural form.
`double`	`NO_UNIQUE_VALUE` Value returned by `getUniqueKeywordValue(String)` when there is no unique value to return.

Fields
`public static final PluralRules`	`DEFAULT` The default rules that accept any number and return `KEYWORD_OTHER`.

Public methods
`static PluralRules`	`createRules(String description)` Creates a PluralRules from a description if it is parsable, otherwise returns null.
`boolean`	`equals(PluralRules rhs)` Returns true if rhs is equal to this.
`boolean`	`equals(Object rhs)` Indicates whether some other object is "equal to" this one.
`static PluralRules`	`forLocale(ULocale locale, PluralRules.PluralType type)` Provides access to the predefined `PluralRules` for a given locale and the plural type.
`static PluralRules`	`forLocale(Locale locale, PluralRules.PluralType type)` Provides access to the predefined `PluralRules` for a given `Locale` and the plural type.
`static PluralRules`	`forLocale(ULocale locale)` Provides access to the predefined cardinal-number `PluralRules` for a given locale.
`static PluralRules`	`forLocale(Locale locale)` Provides access to the predefined cardinal-number `PluralRules` for a given `Locale`.
`Collection<Double>`	`getAllKeywordValues(String keyword)` Returns all the values that trigger this keyword, or null if the number of such values is unlimited.
`Set<String>`	`getKeywords()` Returns a set of all rule keywords used in this `PluralRules` object.
`Collection<Double>`	`getSamples(String keyword)` Returns a list of integer values for which select() would return that keyword, or null if the keyword is not defined.
`double`	`getUniqueKeywordValue(String keyword)` 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.
`static PluralRules`	`parseDescription(String description)` Parses a plural rules description and returns a PluralRules.
`String`	`select(double number)` Given a floating-point number, returns the keyword of the first rule that applies to the number.
`String`	`select(FormattedNumberRange range)` Given a formatted number range, returns the overall plural form of the range.
`String`	`select(FormattedNumber number)` Given a formatted number, returns the keyword of the first rule that applies to the number.
`String`	`toString()` Returns a string representation of the object.

Inherited methods

From class


        
          java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long timeoutMillis, int nanos)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Constants

KEYWORD_FEW

Added in API level 24

public static final String KEYWORD_FEW

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

Constant Value: "few"

KEYWORD_MANY

Added in API level 24

public static final String KEYWORD_MANY

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

Constant Value: "many"

KEYWORD_ONE

Added in API level 24

public static final String KEYWORD_ONE

Common name for the 'singular' plural form.

Constant Value: "one"

KEYWORD_OTHER

Added in API level 24

public static final String KEYWORD_OTHER

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.

Constant Value: "other"

KEYWORD_TWO

Added in API level 24

public static final String KEYWORD_TWO

Common name for the 'dual' plural form.

Constant Value: "two"

KEYWORD_ZERO

Added in API level 24

public static final String KEYWORD_ZERO

Common name for the 'zero' plural form.

Constant Value: "zero"

NO_UNIQUE_VALUE

Added in API level 24

public static final double NO_UNIQUE_VALUE

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

Constant Value: -0.00123456777

Fields

DEFAULT

Added in API level 24

public static final PluralRules DEFAULT

The default rules that accept any number and return KEYWORD_OTHER.

Public methods

createRules

Added in API level 24

public static PluralRules createRules (String description)

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

Parameters
`description`	`String`: the rule description.

Returns
`PluralRules`	the PluralRules

equals

Added in API level 24

public boolean equals (PluralRules rhs)

Returns true if rhs is equal to this.

Parameters
`rhs`	`PluralRules`: the PluralRules to compare to.

Returns
`boolean`	true if this and rhs are equal.

equals

Added in API level 24

public boolean equals (Object rhs)

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
`rhs`	`Object`: the reference object with which to compare.

Returns
`boolean`	`true` if this object is the same as the obj argument; `false` otherwise.

forLocale

Added in API level 24

public static PluralRules forLocale (ULocale locale, 
                PluralRules.PluralType type)

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).

Returns
`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

public static PluralRules forLocale (Locale locale, 
                PluralRules.PluralType type)

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

Parameters
`locale`	`Locale`: The locale for which a `PluralRules` object is returned.
`type`	`PluralRules.PluralType`: The plural type (e.g., cardinal or ordinal).

Returns
`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

public static PluralRules forLocale (ULocale locale)

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

Parameters
`locale`	`ULocale`: The locale for which a `PluralRules` object is returned.

Returns
`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

public static PluralRules forLocale (Locale locale)

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

Parameters
`locale`	`Locale`: The locale for which a `PluralRules` object is returned.

Returns
`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

public Collection<Double> getAllKeywordValues (String keyword)

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

Parameters
`keyword`	`String`: the keyword

Returns
`Collection<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

public Set<String> getKeywords ()

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

Returns
`Set<String>`	The set of keywords.

getSamples

Added in API level 24

public Collection<Double> getSamples (String keyword)

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

Returns
`Collection<Double>`	a list of values matching the keyword.

getUniqueKeywordValue

Added in API level 24

public double getUniqueKeywordValue (String keyword)

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

Returns
`double`	The unique value for the keyword, or NO_UNIQUE_VALUE.

parseDescription

Added in API level 24

public static PluralRules parseDescription (String description)

Parses a plural rules description and returns a PluralRules.

Parameters
`description`	`String`: the rule description.

Returns
`PluralRules`

Throws
`ParseException`	if the description cannot be parsed. The exception index is typically not set, it will be -1.

select

Added in API level 24

public String select (double number)

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.

Returns
`String`	The keyword of the selected rule.

select

Added in API level 33

public String select (FormattedNumberRange range)

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 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.

Returns
`String`	The keyword of the selected rule.

Throws
`UnsupportedOperationException`	If called on an instance without plural ranges data.

select

Added in API level 31

public String select (FormattedNumber number)

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.

Returns
`String`	The keyword of the selected rule.

toString

Added in API level 24

public String toString ()

Returns a string representation of the object.

Returns
`String`	a string representation of the object.