public class PluralRules
extends java.lang.Object
implements java.io.Serializable
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(double)
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, C.11 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 = is_relation | in_relation | within_relation | 'n'is_relation = expr 'is' ('not')? value in_relation = expr ('not')? 'in' range_list within_relation = expr ('not')? 'within' range_list expr = 'n' ('mod' value)? range_list = (range | value) (',' range_list)* value = digit+ digit = 0|1|2|3|4|5|6|7|8|9 range = value'..'value
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).
Modifier and Type | Class and Description |
---|---|
static class |
PluralRules.KeywordStatus
Status of the keyword for the rules, given a set of explicit values.
|
static class |
PluralRules.PluralType
Type of plurals and PluralRules.
|
Modifier and Type | Field and Description |
---|---|
static PluralRules |
DEFAULT
The default rules that accept any number and return
KEYWORD_OTHER . |
static java.lang.String |
KEYWORD_FEW
Common name for the 'paucal' or other special plural form.
|
static java.lang.String |
KEYWORD_MANY
Common name for the arabic (11 to 99) plural form.
|
static java.lang.String |
KEYWORD_ONE
Common name for the 'singular' plural form.
|
static java.lang.String |
KEYWORD_OTHER
Common name for the default plural form.
|
static java.lang.String |
KEYWORD_TWO
Common name for the 'dual' plural form.
|
static java.lang.String |
KEYWORD_ZERO
Common name for the 'zero' plural form.
|
static double |
NO_UNIQUE_VALUE
Value returned by
getUniqueKeywordValue(java.lang.String) when there is no
unique value to return. |
Modifier and Type | Method and Description |
---|---|
static PluralRules |
createRules(java.lang.String description)
Creates a PluralRules from a description if it is parsable,
otherwise returns null.
|
boolean |
equals(java.lang.Object rhs) |
boolean |
equals(PluralRules rhs)
Returns true if rhs is equal to this.
|
static PluralRules |
forLocale(ULocale locale)
Provides access to the predefined cardinal-number
PluralRules for a given
locale. |
static PluralRules |
forLocale(ULocale locale,
PluralRules.PluralType type)
Provides access to the predefined
PluralRules for a given
locale and the plural type. |
java.util.Collection<java.lang.Double> |
getAllKeywordValues(java.lang.String keyword)
Returns all the values that trigger this keyword, or null if the number of such
values is unlimited.
|
static ULocale[] |
getAvailableULocales()
Returns the set of locales for which PluralRules are known.
|
static ULocale |
getFunctionalEquivalent(ULocale locale,
boolean[] isAvailable)
Returns the 'functionally equivalent' locale with respect to
plural rules.
|
java.util.Set<java.lang.String> |
getKeywords()
Returns a set of all rule keywords used in this
PluralRules
object. |
PluralRules.KeywordStatus |
getKeywordStatus(java.lang.String keyword,
int offset,
java.util.Set<java.lang.Double> explicits,
Output<java.lang.Double> uniqueValue)
Find the status for the keyword, given a certain set of explicit values.
|
java.util.Collection<java.lang.Double> |
getSamples(java.lang.String keyword)
Returns a list of values for which select() would return that keyword,
or null if the keyword is not defined.
|
double |
getUniqueKeywordValue(java.lang.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. |
int |
hashCode() |
static PluralRules |
parseDescription(java.lang.String description)
Parses a plural rules description and returns a PluralRules.
|
java.lang.String |
select(double number)
Given a number, returns the keyword of the first rule that applies to
the number.
|
java.lang.String |
toString() |
public static final java.lang.String KEYWORD_ZERO
public static final java.lang.String KEYWORD_ONE
public static final java.lang.String KEYWORD_TWO
public static final java.lang.String KEYWORD_FEW
public static final java.lang.String KEYWORD_MANY
public static final java.lang.String KEYWORD_OTHER
public static final double NO_UNIQUE_VALUE
getUniqueKeywordValue(java.lang.String)
when there is no
unique value to return.public static final PluralRules DEFAULT
KEYWORD_OTHER
.public static PluralRules parseDescription(java.lang.String description) throws java.text.ParseException
description
- the rule description.java.text.ParseException
- if the description cannot be parsed.
The exception index is typically not set, it will be -1.public static PluralRules createRules(java.lang.String description)
description
- the rule description.public static PluralRules forLocale(ULocale locale)
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 http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/language_plural_rules.html
locale
- The locale for which a PluralRules
object is
returned.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.public static PluralRules forLocale(ULocale locale, PluralRules.PluralType type)
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 http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/language_plural_rules.html
locale
- The locale for which a PluralRules
object is
returned.type
- The plural type (e.g., cardinal or ordinal).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.public java.lang.String select(double number)
number
- The number for which the rule has to be determined.public java.util.Set<java.lang.String> getKeywords()
PluralRules
object. The rule "other" is always present by default.public double getUniqueKeywordValue(java.lang.String keyword)
NO_UNIQUE_VALUE
if the keyword matches multiple values or is not defined for this PluralRules.keyword
- the keyword to check for a unique valuepublic java.util.Collection<java.lang.Double> getAllKeywordValues(java.lang.String keyword)
keyword
- the keywordpublic java.util.Collection<java.lang.Double> getSamples(java.lang.String keyword)
keyword
- the keyword to testpublic static ULocale[] getAvailableULocales()
public static ULocale getFunctionalEquivalent(ULocale locale, boolean[] isAvailable)
locale
- the locale to checkisAvailable
- if not null and of length > 0, this will hold 'true' at
index 0 if locale is directly defined (without fallback) as having plural rulespublic java.lang.String toString()
toString
in class java.lang.Object
public int hashCode()
hashCode
in class java.lang.Object
public boolean equals(java.lang.Object rhs)
equals
in class java.lang.Object
public boolean equals(PluralRules rhs)
rhs
- the PluralRules to compare to.public PluralRules.KeywordStatus getKeywordStatus(java.lang.String keyword, int offset, java.util.Set<java.lang.Double> explicits, Output<java.lang.Double> uniqueValue)
keyword
- the particular keyword (call rules.getKeywords() to get the valid ones)offset
- the offset used, or 0.0d if not. Internally, the offset is subtracted from each explicit value before
checking against the keyword values.explicits
- a set of Doubles that are used explicitly (eg [=0], "[=1]"). May be empty or null.uniqueValue
- If non null, set to the unique value.Copyright (c) 2012 IBM Corporation and others.