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SelectFormat

public class SelectFormat
extends Format

java.lang.Object
   ↳ java.text.Format
     ↳ android.icu.text.SelectFormat


SelectFormat supports the creation of internationalized messages by selecting phrases based on keywords. The pattern specifies how to map keywords to phrases and provides a default phrase. The object provided to the format method is a string that's matched against the keywords. If there is a match, the corresponding phrase is selected; otherwise, the default phrase is used.

Using SelectFormat for Gender Agreement

Note: Typically, select formatting is done via MessageFormat with a select argument type, rather than using a stand-alone SelectFormat.

The main use case for the select format is gender based inflection. When names or nouns are inserted into sentences, their gender can affect pronouns, verb forms, articles, and adjectives. Special care needs to be taken for the case where the gender cannot be determined. The impact varies between languages:

  • English has three genders, and unknown gender is handled as a special case. Names use the gender of the named person (if known), nouns referring to people use natural gender, and inanimate objects are usually neutral. The gender only affects pronouns: "he", "she", "it", "they".
  • German differs from English in that the gender of nouns is rather arbitrary, even for nouns referring to people ("Mädchen", girl, is neutral). The gender affects pronouns ("er", "sie", "es"), articles ("der", "die", "das"), and adjective forms ("guter Mann", "gute Frau", "gutes Mädchen").
  • French has only two genders; as in German the gender of nouns is rather arbitrary - for sun and moon, the genders are the opposite of those in German. The gender affects pronouns ("il", "elle"), articles ("le", "la"), adjective forms ("bon", "bonne"), and sometimes verb forms ("allé", "allée").
  • Polish distinguishes five genders (or noun classes), human masculine, animate non-human masculine, inanimate masculine, feminine, and neuter.

Some other languages have noun classes that are not related to gender, but similar in grammatical use. Some African languages have around 20 noun classes.

Note:For the gender of a person in a given sentence, we usually need to distinguish only between female, male and other/unknown.

To enable localizers to create sentence patterns that take their language's gender dependencies into consideration, software has to provide information about the gender associated with a noun or name to MessageFormat. Two main cases can be distinguished:

  • For people, natural gender information should be maintained for each person. Keywords like "male", "female", "mixed" (for groups of people) and "unknown" could be used.
  • For nouns, grammatical gender information should be maintained for each noun and per language, e.g., in resource bundles. The keywords "masculine", "feminine", and "neuter" are commonly used, but some languages may require other keywords.

The resulting keyword is provided to MessageFormat as a parameter separate from the name or noun it's associated with. For example, to generate a message such as "Jean went to Paris", three separate arguments would be provided: The name of the person as argument 0, the gender of the person as argument 1, and the name of the city as argument 2. The sentence pattern for English, where the gender of the person has no impact on this simple sentence, would not refer to argument 1 at all:

{0} went to {2}.

Note: The entire sentence should be included (and partially repeated) inside each phrase. Otherwise translators would have to be trained on how to move bits of the sentence in and out of the select argument of a message. (The examples below do not follow this recommendation!)

The sentence pattern for French, where the gender of the person affects the form of the participle, uses a select format based on argument 1:

{0} est {1, select, female {allée} other {allé}} à {2}.

Patterns can be nested, so that it's possible to handle interactions of number and gender where necessary. For example, if the above sentence should allow for the names of several people to be inserted, the following sentence pattern can be used (with argument 0 the list of people's names, argument 1 the number of people, argument 2 their combined gender, and argument 3 the city name):

{0} {1, plural, 
 one {est {2, select, female {allée} other  {allé}}}
 other {sont {2, select, female {allées} other {allés}}}
 }à {3}.

Patterns and Their Interpretation

The SelectFormat pattern string defines the phrase output for each user-defined keyword. The pattern is a sequence of (keyword, message) pairs. A keyword is a "pattern identifier": [^[[:Pattern_Syntax:][:Pattern_White_Space:]]]+

Each message is a MessageFormat pattern string enclosed in {curly braces}.

You always have to define a phrase for the default keyword other; this phrase is returned when the keyword provided to the format method matches no other keyword. If a pattern does not provide a phrase for other, the method it's provided to returns the error U_DEFAULT_KEYWORD_MISSING.
Pattern_White_Space between keywords and messages is ignored. Pattern_White_Space within a message is preserved and output.

Example:
 MessageFormat msgFmt = new MessageFormat("{0} est " +
     "{1, select, female {allée} other {allé}} à Paris.",
     new ULocale("fr"));
 Object args[] = {"Kirti","female"};
 System.out.println(msgFmt.format(args));
 

Produces the output:
Kirti est allée à Paris.

Summary

Public constructors

SelectFormat(String pattern)

Creates a new SelectFormat for a given pattern string.

Public methods

void applyPattern(String pattern)

Sets the pattern used by this select format.

boolean equals(Object obj)

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

StringBuffer format(Object keyword, StringBuffer toAppendTo, FieldPosition pos)

Selects the phrase for the given keyword.

final String format(String keyword)

Selects the phrase for the given keyword.

int hashCode()

Returns a hash code value for the object.

Object parseObject(String source, ParsePosition pos)

This method is not supported by SelectFormat.

String toPattern()

Returns the pattern for this SelectFormat

String toString()

Returns a string representation of the object.

Inherited methods

Public constructors

SelectFormat

added in API level 24
public SelectFormat (String pattern)

Creates a new SelectFormat for a given pattern string.

Parameters
pattern String: the pattern for this SelectFormat.

Public methods

applyPattern

added in API level 24
public void applyPattern (String pattern)

Sets the pattern used by this select format. Patterns and their interpretation are specified in the class description.

Parameters
pattern String: the pattern for this select format.

Throws
IllegalArgumentException when the pattern is not a valid select format pattern.

equals

added in API level 24
public boolean equals (Object obj)

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.

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
obj Object: the reference object with which to compare.

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

format

added in API level 24
public StringBuffer format (Object keyword, 
                StringBuffer toAppendTo, 
                FieldPosition pos)

Selects the phrase for the given keyword. and appends the formatted message to the given StringBuffer.

Parameters
keyword Object: a phrase selection keyword.

toAppendTo StringBuffer: the selected phrase 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 when the given keyword is not a String or not a "pattern identifier"

format

added in API level 24
public final String format (String keyword)

Selects the phrase for the given keyword.

Parameters
keyword String: a phrase selection keyword.

Returns
String the string containing the formatted select message.

Throws
IllegalArgumentException when the given keyword is not a "pattern identifier"

hashCode

added in API level 24
public 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:

  • 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 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.
  • If two objects are equal according to the equals(Object) method, then calling the hashCode 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(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 Java™ programming language.)

Returns
int a hash code value for this object.

parseObject

added in API level 24
public Object parseObject (String source, 
                ParsePosition pos)

This method is not supported by SelectFormat.

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 supported.

Throws
UnsupportedOperationException thrown always.

toPattern

added in API level 24
public String toPattern ()

Returns the pattern for this SelectFormat

Returns
String the pattern string

toString

added in API level 24
public 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.