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com.ibm.icu.text.SelectFormat Maven / Gradle / Ivy

// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html#License
/*
 *******************************************************************************
 * Copyright (C) 2004-2016, International Business Machines Corporation and    *
 * others. All Rights Reserved.                                                *
 * Copyright (C) 2009 , Yahoo! Inc.                                            *
 *******************************************************************************
 */
package com.ibm.icu.text;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.text.FieldPosition;
import java.text.Format;
import java.text.ParsePosition;

import com.ibm.icu.impl.PatternProps;

/**
 * 
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.
 *
 * @stable ICU 4.4
 */

public class SelectFormat extends Format{
    // Generated by serialver from JDK 1.5
    private static final long serialVersionUID = 2993154333257524984L;

    /*
     * The applied pattern string.
     */
    private String pattern = null;

    /**
     * The MessagePattern which contains the parsed structure of the pattern string.
     */
    transient private MessagePattern msgPattern;
    
    /**
     * Creates a new SelectFormat for a given pattern string.
     * @param  pattern the pattern for this SelectFormat.
     * @stable ICU 4.4
     */
    public SelectFormat(String pattern) {
        applyPattern(pattern);
    }

    /*
     * Resets the SelectFormat object.
     */
    private void reset() {
        pattern = null;
        if(msgPattern != null) {
            msgPattern.clear();
        }
    }

    /**
     * Sets the pattern used by this select format.
     * Patterns and their interpretation are specified in the class description.
     *
     * @param pattern the pattern for this select format.
     * @throws IllegalArgumentException when the pattern is not a valid select format pattern.
     * @stable ICU 4.4
     */
    public void applyPattern(String pattern) {
        this.pattern = pattern;
        if (msgPattern == null) {
            msgPattern = new MessagePattern();
        }
        try {
            msgPattern.parseSelectStyle(pattern);
        } catch(RuntimeException e) {
            reset();
            throw e;
        }
    }

    /**
     * Returns the pattern for this SelectFormat
     *
     * @return the pattern string
     * @stable ICU 4.4
     */
    public String toPattern() {
        return pattern;
    }

    /**
     * Finds the SelectFormat sub-message for the given keyword, or the "other" sub-message.
     * @param pattern A MessagePattern.
     * @param partIndex the index of the first SelectFormat argument style part.
     * @param keyword a keyword to be matched to one of the SelectFormat argument's keywords.
     * @return the sub-message start part index.
     */
    /*package*/ static int findSubMessage(MessagePattern pattern, int partIndex, String keyword) {
        int count=pattern.countParts();
        int msgStart=0;
        // Iterate over (ARG_SELECTOR, message) pairs until ARG_LIMIT or end of select-only pattern.
        do {
            MessagePattern.Part part=pattern.getPart(partIndex++);
            MessagePattern.Part.Type type=part.getType();
            if(type==MessagePattern.Part.Type.ARG_LIMIT) {
                break;
            }
            assert type==MessagePattern.Part.Type.ARG_SELECTOR;
            // part is an ARG_SELECTOR followed by a message
            if(pattern.partSubstringMatches(part, keyword)) {
                // keyword matches
                return partIndex;
            } else if(msgStart==0 && pattern.partSubstringMatches(part, "other")) {
                msgStart=partIndex;
            }
            partIndex=pattern.getLimitPartIndex(partIndex);
        } while(++partIndexStringBuffer.
     * @param keyword a phrase selection keyword.
     * @param toAppendTo the selected phrase will be appended to this
     *        StringBuffer.
     * @param pos will be ignored by this method.
     * @throws IllegalArgumentException when the given keyword is not a String
     *         or not a "pattern identifier"
     * @return the string buffer passed in as toAppendTo, with formatted text
     *         appended.
     * @stable ICU 4.4
     */
    public StringBuffer format(Object keyword, StringBuffer toAppendTo,
            FieldPosition pos) {
        if (keyword instanceof String) {
            toAppendTo.append(format( (String)keyword));
        }else{
            throw new IllegalArgumentException("'" + keyword + "' is not a String");
        }
        return toAppendTo;
    }

    /**
     * This method is not supported by SelectFormat.
     * @param source the string to be parsed.
     * @param pos 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 nothing because this method is not supported.
     * @throws UnsupportedOperationException thrown always.
     * @stable ICU 4.4
     */
    public Object parseObject(String source, ParsePosition pos) {
        throw new UnsupportedOperationException();
    }

    /**
     * {@inheritDoc}
     * @stable ICU 4.4
     */
    @Override
    public boolean equals(Object obj) {
        if(this == obj) {
            return true;
        }
        if(obj == null || getClass() != obj.getClass()) {
            return false;
        }
        SelectFormat sf = (SelectFormat) obj;
        return msgPattern == null ? sf.msgPattern == null : msgPattern.equals(sf.msgPattern);
    }

    /**
     * {@inheritDoc}
     * @stable ICU 4.4
     */
    @Override
    public int hashCode() {
        if (pattern != null) {
            return pattern.hashCode();
        }
        return 0;
    }

    /**
     * {@inheritDoc}
     * @stable ICU 4.4
     */
    @Override
    public String toString() {
        return "pattern='" + pattern + "'";
    }

    private void readObject(ObjectInputStream in)
        throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        if (pattern != null) {
            applyPattern(pattern);
        }
    }
}