PluralFormat
open class PluralFormat : UFormat
kotlin.Any | |||
↳ | java.text.Format | ||
↳ | android.icu.text.UFormat | ||
↳ | android.icu.text.PluralFormat |
PluralFormat
supports the creation of internationalized messages with plural inflection. It is based on plural selection, i.e. the caller specifies messages for each plural case that can appear in the user's language and the PluralFormat
selects the appropriate message based on the number.
The Problem of Plural Forms in Internationalized Messages
Different languages have different ways to inflect plurals. Creating internationalized messages that include plural forms is only feasible when the framework is able to handle plural forms of all languages correctly. ChoiceFormat
doesn't handle this well, because it attaches a number interval to each message and selects the message whose interval contains a given number. This can only handle a finite number of intervals. But in some languages, like Polish, one plural case applies to infinitely many intervals (e.g., the paucal case applies to numbers ending with 2, 3, or 4 except those ending with 12, 13, or 14). Thus ChoiceFormat
is not adequate.
PluralFormat
deals with this by breaking the problem into two parts:
- It uses
PluralRules
that can define more complex conditions for a plural case than just a single interval. These plural rules define both what plural cases exist in a language, and to which numbers these cases apply. - It provides predefined plural rules for many languages. Thus, the programmer need not worry about the plural cases of a language and does not have to define the plural cases; they can simply use the predefined keywords. The whole plural formatting of messages can be done using localized patterns from resource bundles. For predefined plural rules, see the CLDR Language Plural Rules page at https://unicode-org.github.io/cldr-staging/charts/latest/supplemental/language_plural_rules.html
Usage of PluralFormat
Note: Typically, plural formatting is done via MessageFormat
with a plural
argument type, rather than using a stand-alone PluralFormat
.
This discussion assumes that you use PluralFormat
with a predefined set of plural rules. You can create one using one of the constructors that takes a ULocale
object. To specify the message pattern, you can either pass it to the constructor or set it explicitly using the applyPattern()
method. The format()
method takes a number object and selects the message of the matching plural case. This message will be returned.
Patterns and Their Interpretation
The pattern text defines the message output for each plural case of the specified locale. Syntax:
pluralStyle = [offsetValue] (selector '{' message '}')+ offsetValue = "offset:" number selector = explicitValue | keyword explicitValue = '=' number // adjacent, no white space in between keyword = [^[[:Pattern_Syntax:][:Pattern_White_Space:]]]+ message: see <code><a docref="android.icu.text.MessageFormat">MessageFormat</a></code>
There are 6 predefined case keywords in CLDR/ICU - 'zero', 'one', 'two', 'few', 'many' and 'other'. You always have to define a message text for the default plural case "other
" which is contained in every rule set. If you do not specify a message text for a particular plural case, the message text of the plural case "other
" gets assigned to this plural case.
When formatting, the input number is first matched against the explicitValue clauses. If there is no exact-number match, then a keyword is selected by calling the PluralRules
with the input number minus the offset. (The offset defaults to 0 if it is omitted from the pattern string.) If there is no clause with that keyword, then the "other" clauses is returned.
An unquoted pound sign () in the selected sub-message itself (i.e., outside of arguments nested in the sub-message) is replaced by the input number minus the offset. The number-minus-offset value is formatted using a
NumberFormat
for the PluralFormat
's locale. If you need special number formatting, you have to use a MessageFormat
and explicitly specify a NumberFormat
argument. Note: That argument is formatting without subtracting the offset! If you need a custom format and have a non-zero offset, then you need to pass the number-minus-offset value as a separate parameter.
For a usage example, see the MessageFormat
class documentation.
Defining Custom Plural Rules
If you need to use PluralFormat
with custom rules, you can create a PluralRules
object and pass it to PluralFormat
's constructor. If you also specify a locale in this constructor, this locale will be used to format the number in the message texts.
For more information about PluralRules
, see PluralRules
.
Summary
Public constructors | |
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Creates a new cardinal-number |
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PluralFormat(ulocale: ULocale!) Creates a new cardinal-number |
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PluralFormat(locale: Locale!) Creates a new cardinal-number |
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PluralFormat(rules: PluralRules!) Creates a new cardinal-number |
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PluralFormat(ulocale: ULocale!, rules: PluralRules!) Creates a new cardinal-number |
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PluralFormat(locale: Locale!, rules: PluralRules!) Creates a new cardinal-number |
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PluralFormat(ulocale: ULocale!, type: PluralRules.PluralType!) Creates a new |
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PluralFormat(locale: Locale!, type: PluralRules.PluralType!) Creates a new |
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PluralFormat(pattern: String!) Creates a new cardinal-number |
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PluralFormat(ulocale: ULocale!, pattern: String!) Creates a new cardinal-number |
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PluralFormat(rules: PluralRules!, pattern: String!) Creates a new cardinal-number |
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PluralFormat(ulocale: ULocale!, rules: PluralRules!, pattern: String!) Creates a new cardinal-number |
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PluralFormat(ulocale: ULocale!, type: PluralRules.PluralType!, pattern: String!) Creates a new |
Public methods | |
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open Unit |
applyPattern(pattern: String!) Sets the pattern used by this plural format. |
open Boolean |
Indicates whether some other object is "equal to" this one. |
open Boolean |
equals(rhs: PluralFormat!) Returns true if this equals the provided PluralFormat. |
String! |
Formats a plural message for a given number. |
open StringBuffer! |
format(number: Any!, toAppendTo: StringBuffer!, pos: FieldPosition!) Formats a plural message for a given number and appends the formatted message to the given |
open Int |
hashCode() Returns a hash code value for the object. |
open Number! |
parse(text: String!, parsePosition: ParsePosition!) This method is not yet supported by |
open Any! |
parseObject(source: String!, pos: ParsePosition!) This method is not yet supported by |
open Unit |
setNumberFormat(format: NumberFormat!) Sets the number format used by this formatter. |
open String! |
Returns the pattern for this PluralFormat. |
open String |
toString() Returns a string representation of the object. |
Public constructors
PluralFormat
PluralFormat()
Creates a new cardinal-number PluralFormat
for the default FORMAT
locale. This locale will be used to get the set of plural rules and for standard number formatting.
PluralFormat
PluralFormat(ulocale: ULocale!)
Creates a new cardinal-number PluralFormat
for a given locale.
Parameters | |
---|---|
ulocale |
ULocale!: the PluralFormat will be configured with rules for this locale. This locale will also be used for standard number formatting. |
PluralFormat
PluralFormat(locale: Locale!)
Creates a new cardinal-number PluralFormat
for a given java.util.Locale
.
Parameters | |
---|---|
locale |
Locale!: the PluralFormat will be configured with rules for this locale. This locale will also be used for standard number formatting. |
PluralFormat
PluralFormat(rules: PluralRules!)
Creates a new cardinal-number PluralFormat
for a given set of rules. The standard number formatting will be done using the default FORMAT
locale.
Parameters | |
---|---|
rules |
PluralRules!: defines the behavior of the PluralFormat object. |
PluralFormat
PluralFormat(
ulocale: ULocale!,
rules: PluralRules!)
Creates a new cardinal-number PluralFormat
for a given set of rules. The standard number formatting will be done using the given locale.
Parameters | |
---|---|
ulocale |
ULocale!: the default number formatting will be done using this locale. |
rules |
PluralRules!: defines the behavior of the PluralFormat object. |
PluralFormat
PluralFormat(
locale: Locale!,
rules: PluralRules!)
Creates a new cardinal-number PluralFormat
for a given set of rules. The standard number formatting will be done using the given locale.
Parameters | |
---|---|
locale |
Locale!: the default number formatting will be done using this locale. |
rules |
PluralRules!: defines the behavior of the PluralFormat object. |
PluralFormat
PluralFormat(
ulocale: ULocale!,
type: PluralRules.PluralType!)
Creates a new PluralFormat
for the plural type. The standard number formatting will be done using the given locale.
Parameters | |
---|---|
ulocale |
ULocale!: the default number formatting will be done using this locale. |
type |
PluralRules.PluralType!: The plural type (e.g., cardinal or ordinal). |
PluralFormat
PluralFormat(
locale: Locale!,
type: PluralRules.PluralType!)
Creates a new PluralFormat
for the plural type. The standard number formatting will be done using the given java.util.Locale
.
Parameters | |
---|---|
locale |
Locale!: the default number formatting will be done using this locale. |
type |
PluralRules.PluralType!: The plural type (e.g., cardinal or ordinal). |
PluralFormat
PluralFormat(pattern: String!)
Creates a new cardinal-number PluralFormat
for a given pattern string. The default FORMAT
locale will be used to get the set of plural rules and for standard number formatting.
Parameters | |
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pattern |
String!: the pattern for this PluralFormat . |
Exceptions | |
---|---|
java.lang.IllegalArgumentException |
if the pattern is invalid. |
PluralFormat
PluralFormat(
ulocale: ULocale!,
pattern: String!)
Creates a new cardinal-number PluralFormat
for a given pattern string and locale. The locale will be used to get the set of plural rules and for standard number formatting.
Example code:
Parameters | |
---|---|
ulocale |
ULocale!: the PluralFormat will be configured with rules for this locale. This locale will also be used for standard number formatting. |
pattern |
String!: the pattern for this PluralFormat . |
Exceptions | |
---|---|
java.lang.IllegalArgumentException |
if the pattern is invalid. |
PluralFormat
PluralFormat(
rules: PluralRules!,
pattern: String!)
Creates a new cardinal-number PluralFormat
for a given set of rules and a pattern. The standard number formatting will be done using the default FORMAT
locale.
Parameters | |
---|---|
rules |
PluralRules!: defines the behavior of the PluralFormat object. |
pattern |
String!: the pattern for this PluralFormat . |
Exceptions | |
---|---|
java.lang.IllegalArgumentException |
if the pattern is invalid. |
PluralFormat
PluralFormat(
ulocale: ULocale!,
rules: PluralRules!,
pattern: String!)
Creates a new cardinal-number PluralFormat
for a given set of rules, a pattern and a locale.
Parameters | |
---|---|
ulocale |
ULocale!: the PluralFormat will be configured with rules for this locale. This locale will also be used for standard number formatting. |
rules |
PluralRules!: defines the behavior of the PluralFormat object. |
pattern |
String!: the pattern for this PluralFormat . |
Exceptions | |
---|---|
java.lang.IllegalArgumentException |
if the pattern is invalid. |
PluralFormat
PluralFormat(
ulocale: ULocale!,
type: PluralRules.PluralType!,
pattern: String!)
Creates a new PluralFormat
for a plural type, a pattern and a locale.
Parameters | |
---|---|
ulocale |
ULocale!: the PluralFormat will be configured with rules for this locale. This locale will also be used for standard number formatting. |
type |
PluralRules.PluralType!: The plural type (e.g., cardinal or ordinal). |
pattern |
String!: the pattern for this PluralFormat . |
Exceptions | |
---|---|
java.lang.IllegalArgumentException |
if the pattern is invalid. |
Public methods
applyPattern
open fun applyPattern(pattern: String!): Unit
Sets the pattern used by this plural format. The method parses the pattern and creates a map of format strings for the plural rules. Patterns and their interpretation are specified in the class description.
Parameters | |
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pattern |
String!: the pattern for this plural format. |
Exceptions | |
---|---|
java.lang.IllegalArgumentException |
if the pattern is invalid. |
equals
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 returntrue
. - It is symmetric: for any non-null reference values
x
andy
,x.equals(y)
should returntrue
if and only ify.equals(x)
returnstrue
. - It is transitive: for any non-null reference values
x
,y
, andz
, ifx.equals(y)
returnstrue
andy.equals(z)
returnstrue
, thenx.equals(z)
should returntrue
. - It is consistent: for any non-null reference values
x
andy
, multiple invocations ofx.equals(y)
consistently returntrue
or consistently returnfalse
, provided no information used inequals
comparisons on the objects is modified. - For any non-null reference value
x
,x.equals(null)
should returnfalse
.
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
open fun equals(rhs: PluralFormat!): Boolean
Returns true if this equals the provided PluralFormat.
Parameters | |
---|---|
rhs |
PluralFormat!: the PluralFormat to compare against |
Return | |
---|---|
Boolean |
true if this equals rhs |
format
fun format(number: Double): String!
Formats a plural message for a given number.
Parameters | |
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number |
Double: a number for which the plural message should be formatted. If no pattern has been applied to this PluralFormat object yet, the formatted number will be returned. |
Return | |
---|---|
String! |
the string containing the formatted plural message. |
format
open fun format(
number: Any!,
toAppendTo: StringBuffer!,
pos: FieldPosition!
): StringBuffer!
Formats a plural message for a given number and appends the formatted message to the given StringBuffer
.
Parameters | |
---|---|
obj |
The object to format |
toAppendTo |
StringBuffer!: the formatted message will be appended to this StringBuffer . |
pos |
FieldPosition!: will be ignored by this method. |
number |
Any!: a number object (instance of Number for which the plural message should be formatted. If no pattern has been applied to this PluralFormat object yet, the formatted number will be returned. Note: If this object is not an instance of Number , the toAppendTo will not be modified. |
Return | |
---|---|
StringBuffer! |
the string buffer passed in as toAppendTo, with formatted text appended. |
Exceptions | |
---|---|
java.lang.NullPointerException |
if toAppendTo or pos is null |
java.lang.IllegalArgumentException |
if number is not an instance of Number |
hashCode
open fun hashCode(): Int
Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by java.util.HashMap
.
The general contract of hashCode
is:
- Whenever it is invoked on the same object more than once during an execution of a Java application, the
hashCode
method must consistently return the same integer, provided no information used inequals
comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application. - If two objects are equal according to the
equals
method, then calling thehashCode
method on each of the two objects must produce the same integer result. - It is not required that if two objects are unequal according to the
equals
method, then calling thehashCode
method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.
Return | |
---|---|
Int |
a hash code value for this object. |
parse
open fun parse(
text: String!,
parsePosition: ParsePosition!
): Number!
This method is not yet supported by PluralFormat
.
Parameters | |
---|---|
text |
String!: the string to be parsed. |
parsePosition |
ParsePosition!: defines the position where parsing is to begin, and upon return, the position where parsing left off. If the position has not changed upon return, then parsing failed. |
Return | |
---|---|
Number! |
nothing because this method is not yet implemented. |
Exceptions | |
---|---|
java.lang.UnsupportedOperationException |
will always be thrown by this method. |
parseObject
open fun parseObject(
source: String!,
pos: ParsePosition!
): Any!
This method is not yet supported by PluralFormat
.
Parameters | |
---|---|
source |
String!: the string to be parsed. |
pos |
ParsePosition!: defines the position where parsing is to begin, and upon return, the position where parsing left off. If the position has not changed upon return, then parsing failed. |
Return | |
---|---|
Any! |
nothing because this method is not yet implemented. |
Exceptions | |
---|---|
java.lang.NullPointerException |
if source or pos is null. |
java.lang.UnsupportedOperationException |
will always be thrown by this method. |
setNumberFormat
open fun setNumberFormat(format: NumberFormat!): Unit
Sets the number format used by this formatter. You only need to call this if you want a different number format than the default formatter for the locale.
Parameters | |
---|---|
format |
NumberFormat!: the number format to use. |
toPattern
open fun toPattern(): String!
Returns the pattern for this PluralFormat.
Return | |
---|---|
String! |
the pattern string |
toString
open fun toString(): String
Returns a string representation of the object.
Return | |
---|---|
String |
a string representation of the object. |