public class PluralFormat
extends UFormat
java.lang.Object | |||
↳ | 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.
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:
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. 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.
The pattern text defines the message output for each plural case of the specified locale. Syntax:
Pattern_White_Space between syntax elements is ignored, except between the {curly braces} and their sub-message, and between the '=' and the number of an explicitValue.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: seeMessageFormat
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.
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
.
Public constructors |
|
---|---|
PluralFormat() Creates a new cardinal-number |
|
PluralFormat(ULocale ulocale) Creates a new cardinal-number |
|
PluralFormat(Locale locale) Creates a new cardinal-number |
|
PluralFormat(PluralRules rules) Creates a new cardinal-number |
|
PluralFormat(ULocale ulocale, PluralRules rules) Creates a new cardinal-number |
|
PluralFormat(Locale locale, PluralRules rules) Creates a new cardinal-number |
|
PluralFormat(ULocale ulocale, PluralRules.PluralType type) Creates a new |
|
PluralFormat(Locale locale, PluralRules.PluralType type) Creates a new |
|
PluralFormat(String pattern) Creates a new cardinal-number |
|
PluralFormat(ULocale ulocale, String pattern) Creates a new cardinal-number |
|
PluralFormat(PluralRules rules, String pattern) Creates a new cardinal-number |
|
PluralFormat(ULocale ulocale, PluralRules rules, String pattern) Creates a new cardinal-number |
|
PluralFormat(ULocale ulocale, PluralRules.PluralType type, String pattern) Creates a new |
Public methods |
|
---|---|
void |
applyPattern(String pattern) Sets the pattern used by this plural format. |
boolean |
equals(Object rhs) Indicates whether some other object is "equal to" this one. |
boolean |
equals(PluralFormat rhs) Returns true if this equals the provided PluralFormat. |
final String |
format(double number) Formats a plural message for a given number. |
StringBuffer |
format(Object number, StringBuffer toAppendTo, FieldPosition pos) Formats a plural message for a given number and appends the formatted message to the given |
int |
hashCode() Returns a hash code value for the object. |
Number |
parse(String text, ParsePosition parsePosition) This method is not yet supported by |
Object |
parseObject(String source, ParsePosition pos) This method is not yet supported by |
void |
setNumberFormat(NumberFormat format) Sets the number format used by this formatter. |
String |
toPattern() Returns the pattern for this PluralFormat. |
String |
toString() Returns a string representation of the object. |
Inherited methods |
|
---|---|
![]() java.text.Format
|
|
![]() java.lang.Object
|
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.
See also:
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 (Locale locale)
Creates a new cardinal-number PluralFormat
for a given 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 (PluralRules rules)
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. |
See also:
PluralFormat (ULocale ulocale, PluralRules rules)
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 (Locale locale, PluralRules rules)
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 (ULocale ulocale, PluralRules.PluralType type)
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 (Locale locale, PluralRules.PluralType type)
Creates a new PluralFormat
for the plural type. The standard number formatting will be done using the given 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 (String pattern)
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 | |
---|---|
pattern |
String : the pattern for this PluralFormat . |
Throws | |
---|---|
IllegalArgumentException |
if the pattern is invalid. |
See also:
PluralFormat (ULocale ulocale, String pattern)
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:
ULocale locEn = new ULocale("en"); ULocale locSl = new ULocale("sl"); String patEn = "one{dog} other{dogs}"; // English 'dog' String patSl = "one{pes} two{psa} few{psi} other{psov}"; // Slovenian translation of dog in Plural Form // Create a new PluralFormat for a given locale locale and pattern string PluralFormat plfmtEn = new PluralFormat(locEn, patEn); PluralFormat plfmtSl = new PluralFormat(locSl, patSl); // Constructs a MessageFormat for the specified locale and pattern. MessageFormat msgfmtEn = new MessageFormat("{0,number} {1}", locEn); MessageFormat msgfmtSl = new MessageFormat("{0,number} {1}", locSl); final int[] numbers = {0, 1, 2, 3, 4, 5, 10, 100, 101, 102}; System.out.println("Output by using PluralFormat and MessageFormat API\n"); System.out.printf("%-16s%-16s%-16s\n", "Number", "English", "Slovenian"); // Use MessageFormat.format () to format the objects and appends to the given StringBuffer for (int num : numbers) { StringBuffer msgEn = new StringBuffer(); StringBuffer msgSl = new StringBuffer(); msgfmtEn.format(new Object[] {num, plfmtEn.format(num)}, msgEn, new FieldPosition(0)); msgfmtSl.format(new Object[] {num, plfmtSl.format(num)}, msgSl, new FieldPosition(0)); System.out.printf("%-16s%-16s%-16s\n", num, msgEn, msgSl); } System.out.println(); // Equivalent code with message format pattern String msgPatEn = "{0,plural, one{# dog} other{# dogs}}"; String msgPatSl = "{0,plural, one{# pes} two{# psa} few{# psi} other{# psov}}"; MessageFormat altMsgfmtEn = new MessageFormat(msgPatEn, locEn); MessageFormat altMsgfmtSl = new MessageFormat(msgPatSl, locSl); System.out.println("Same Output by using MessageFormat API only\n"); System.out.printf("%-16s%-16s%-16s\n", "Number", "English", "Slovenian"); for (int num : numbers) { StringBuffer msgEn = new StringBuffer(); StringBuffer msgSl = new StringBuffer(); altMsgfmtEn.format(new Object[] {num}, msgEn, new FieldPosition(0)); altMsgfmtSl.format(new Object[] {num}, msgSl, new FieldPosition(0)); System.out.printf("%-16s%-16s%-16s\n", num, msgEn, msgSl); } /** output of the sample code: ******************************************************************** Number English Slovenian 0 0 dogs 0 psov 1 1 dog 1 pes 2 2 dogs 2 psa 3 3 dogs 3 psi 4 4 dogs 4 psi 5 5 dogs 5 psov 10 10 dogs 10 psov 100 100 dogs 100 psov 101 101 dogs 101 pes 102 102 dogs 102 psa *******************************************************************/
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 . |
Throws | |
---|---|
IllegalArgumentException |
if the pattern is invalid. |
PluralFormat (PluralRules rules, String pattern)
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 . |
Throws | |
---|---|
IllegalArgumentException |
if the pattern is invalid. |
See also:
PluralFormat (ULocale ulocale, PluralRules rules, String pattern)
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 . |
Throws | |
---|---|
IllegalArgumentException |
if the pattern is invalid. |
PluralFormat (ULocale ulocale, PluralRules.PluralType type, String pattern)
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 . |
Throws | |
---|---|
IllegalArgumentException |
if the pattern is invalid. |
void applyPattern (String pattern)
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 | |
---|---|
pattern |
String : the pattern for this plural format. |
Throws | |
---|---|
IllegalArgumentException |
if the pattern is invalid. |
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:
x
, x.equals(x)
should return true
. x
and y
, x.equals(y)
should return true
if and only if y.equals(x)
returns true
. x
, y
, and z
, if x.equals(y)
returns true
and y.equals(z)
returns true
, then x.equals(z)
should return true
. 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. x
, x.equals(null)
should return false
. The equals
method for class Object
implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x
and y
, this method returns true
if and only if x
and y
refer to the same object (x == y
has the value true
).
Note that it is generally necessary to override the hashCode
method whenever this method is overridden, so as to maintain the general contract for the hashCode
method, which states that equal objects must have equal hash codes.
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. |
boolean equals (PluralFormat rhs)
Returns true if this equals the provided PluralFormat.
Parameters | |
---|---|
rhs |
PluralFormat : the PluralFormat to compare against |
Returns | |
---|---|
boolean |
true if this equals rhs |
String format (double number)
Formats a plural message for a given number.
Parameters | |
---|---|
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. |
Returns | |
---|---|
String |
the string containing the formatted plural message. |
StringBuffer format (Object number, StringBuffer toAppendTo, FieldPosition pos)
Formats a plural message for a given number and appends the formatted message to the given StringBuffer
.
Parameters | |
---|---|
number |
Object : 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. |
toAppendTo |
StringBuffer : the formatted message will be appended to this StringBuffer . |
pos |
FieldPosition : will be ignored by this method. |
Returns | |
---|---|
StringBuffer |
the string buffer passed in as toAppendTo, with formatted text appended. |
Throws | |
---|---|
IllegalArgumentException |
if number is not an instance of Number |
int hashCode ()
Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap
.
The general contract of hashCode
is:
hashCode
method must consistently return the same integer, provided no information used in equals
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. equals(Object)
method, then calling the hashCode
method on each of the two objects must produce the same integer result. equals(java.lang.Object)
method, then calling the hashCode
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. As much as is reasonably practical, the hashCode method defined by class Object
does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the JavaTM programming language.)
Returns | |
---|---|
int |
a hash code value for this object. |
Number parse (String text, ParsePosition parsePosition)
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. |
Returns | |
---|---|
Number |
nothing because this method is not yet implemented. |
Throws | |
---|---|
UnsupportedOperationException |
will always be thrown by this method. |
Object parseObject (String source, ParsePosition pos)
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. |
Returns | |
---|---|
Object |
nothing because this method is not yet implemented. |
Throws | |
---|---|
UnsupportedOperationException |
will always be thrown by this method. |
void setNumberFormat (NumberFormat format)
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. |
String toPattern ()
Returns the pattern for this PluralFormat.
Returns | |
---|---|
String |
the pattern string |
String toString ()
Returns a string representation of the object. In general, the toString
method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.
The toString
method for class Object
returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@
', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:
getClass().getName() + '@' + Integer.toHexString(hashCode())
Returns | |
---|---|
String |
a string representation of the object. |