Class LocaleMatcher

java.lang.Object
com.ibm.icu.util.LocaleMatcher

public final class LocaleMatcher extends Object
Immutable class that picks the best match between a user's desired locales and an application's supported locales.

Example:

 LocaleMatcher matcher = LocaleMatcher.builder().setSupportedLocales("fr, en-GB, en").build();
 Locale bestSupported = matcher.getBestLocale(Locale.US);  // "en"
 

A matcher takes into account when languages are close to one another, such as Danish and Norwegian, and when regional variants are close, like en-GB and en-AU as opposed to en-US.

If there are multiple supported locales with the same (language, script, region) likely subtags, then the current implementation returns the first of those locales. It ignores variant subtags (except for pseudolocale variants) and extensions. This may change in future versions.

For example, the current implementation does not distinguish between de, de-DE, de-Latn, de-1901, de-u-co-phonebk.

If you prefer one equivalent locale over another, then provide only the preferred one, or place it earlier in the list of supported locales.

Otherwise, the order of supported locales may have no effect on the best-match results. The current implementation compares each desired locale with supported locales in the following order: 1. Default locale, if supported; 2. CLDR "paradigm locales" like en-GB and es-419; 3. other supported locales. This may change in future versions.

Often a product will just need one matcher instance, built with the languages that it supports. However, it may want multiple instances with different default languages based on additional information, such as the domain.

This class is not intended for public subclassing.

  • Field Details

    • UND_LSR

      private static final LSR UND_LSR
    • UND_ULOCALE

      private static final ULocale UND_ULOCALE
    • UND_LOCALE

      private static final Locale UND_LOCALE
    • EMPTY_LOCALE

      private static final Locale EMPTY_LOCALE
    • TRACE_MATCHER

      private static final boolean TRACE_MATCHER
      See Also:
    • thresholdDistance

      private final int thresholdDistance
    • demotionPerDesiredLocale

      private final int demotionPerDesiredLocale
    • favorSubtag

      private final LocaleMatcher.FavorSubtag favorSubtag
    • direction

      private final LocaleMatcher.Direction direction
    • supportedULocales

      private final ULocale[] supportedULocales
    • supportedLocales

      private final Locale[] supportedLocales
    • supportedLsrToIndex

      private final Map<LSR,Integer> supportedLsrToIndex
    • supportedLSRs

      private final LSR[] supportedLSRs
    • supportedIndexes

      private final int[] supportedIndexes
    • supportedLSRsLength

      private final int supportedLSRsLength
    • defaultULocale

      private final ULocale defaultULocale
    • defaultLocale

      private final Locale defaultLocale
  • Constructor Details

    • LocaleMatcher

      public LocaleMatcher(LocalePriorityList supportedLocales)
      Copies the supported locales, preserving iteration order, and constructs a LocaleMatcher. The first locale is used as the default locale for when there is no good match.
      Parameters:
      supportedLocales - list of locales
    • LocaleMatcher

      public LocaleMatcher(String supportedLocales)
      Parses the string like LocalePriorityList does and constructs a LocaleMatcher for the supported locales parsed from the string. The first one (in LocalePriorityList iteration order) is used as the default locale for when there is no good match.
      Parameters:
      supportedLocales - the string of locales to set, to be parsed like LocalePriorityList does
    • LocaleMatcher

      private LocaleMatcher(LocaleMatcher.Builder builder)
  • Method Details

    • builder

      public static LocaleMatcher.Builder builder()
      Returns a builder used in chaining parameters for building a LocaleMatcher.
      Returns:
      a new Builder object
    • putIfAbsent

      private final int putIfAbsent(LSR lsr, int i, int suppLength)
    • getMaximalLsrOrUnd

      private static final LSR getMaximalLsrOrUnd(ULocale locale)
    • getMaximalLsrOrUnd

      private static final LSR getMaximalLsrOrUnd(Locale locale)
    • getBestMatch

      public ULocale getBestMatch(ULocale desiredLocale)
      Returns the supported locale which best matches the desired locale.
      Parameters:
      desiredLocale - Typically a user's language.
      Returns:
      the best-matching supported locale.
    • getBestMatch

      public ULocale getBestMatch(Iterable<ULocale> desiredLocales)
      Returns the supported locale which best matches one of the desired locales.
      Parameters:
      desiredLocales - Typically a user's languages, in order of preference (descending). (In ICU 4.4..63 this parameter had type LocalePriorityList.)
      Returns:
      the best-matching supported locale.
    • getBestMatch

      public ULocale getBestMatch(String desiredLocaleList)
      Parses the string like LocalePriorityList does and returns the supported locale which best matches one of the desired locales.
      Parameters:
      desiredLocaleList - Typically a user's languages, as a string which is to be parsed like LocalePriorityList does.
      Returns:
      the best-matching supported locale.
    • getBestLocale

      public Locale getBestLocale(Locale desiredLocale)
      Returns the supported locale which best matches the desired locale.
      Parameters:
      desiredLocale - Typically a user's language.
      Returns:
      the best-matching supported locale.
    • getBestLocale

      public Locale getBestLocale(Iterable<Locale> desiredLocales)
      Returns the supported locale which best matches one of the desired locales.
      Parameters:
      desiredLocales - Typically a user's languages, in order of preference (descending).
      Returns:
      the best-matching supported locale.
    • defaultResult

      private LocaleMatcher.Result defaultResult()
    • makeResult

      private LocaleMatcher.Result makeResult(ULocale desiredLocale, LocaleMatcher.ULocaleLsrIterator lsrIter, int suppIndex)
    • makeResult

      private LocaleMatcher.Result makeResult(Locale desiredLocale, LocaleMatcher.LocaleLsrIterator lsrIter, int suppIndex)
    • getBestMatchResult

      public LocaleMatcher.Result getBestMatchResult(ULocale desiredLocale)
      Returns the best match between the desired locale and the supported locales.
      Parameters:
      desiredLocale - Typically a user's language.
      Returns:
      the best-matching pair of the desired and a supported locale.
    • getBestMatchResult

      public LocaleMatcher.Result getBestMatchResult(Iterable<ULocale> desiredLocales)
      Returns the best match between the desired and supported locales.
      Parameters:
      desiredLocales - Typically a user's languages, in order of preference (descending).
      Returns:
      the best-matching pair of a desired and a supported locale.
    • getBestLocaleResult

      public LocaleMatcher.Result getBestLocaleResult(Locale desiredLocale)
      Returns the best match between the desired locale and the supported locales.
      Parameters:
      desiredLocale - Typically a user's language.
      Returns:
      the best-matching pair of the desired and a supported locale.
    • getBestLocaleResult

      public LocaleMatcher.Result getBestLocaleResult(Iterable<Locale> desiredLocales)
      Returns the best match between the desired and supported locales.
      Parameters:
      desiredLocales - Typically a user's languages, in order of preference (descending).
      Returns:
      the best-matching pair of a desired and a supported locale.
    • getBestSuppIndex

      private int getBestSuppIndex(LSR desiredLSR, LocaleMatcher.LsrIterator remainingIter)
      Parameters:
      desiredLSR - The first desired locale's LSR.
      remainingIter - Remaining desired LSRs, null or empty if none.
      Returns:
      the index of the best-matching supported locale, or -1 if there is no good match.
    • isMatch

      public boolean isMatch(Locale desired, Locale supported)
      Returns true if the pair of locales matches acceptably. This is influenced by Builder options such as setDirection(), setFavorSubtag(), and setMaxDistance().
      Parameters:
      desired - The desired locale.
      supported - The supported locale.
      Returns:
      true if the pair of locales matches acceptably.
    • isMatch

      public boolean isMatch(ULocale desired, ULocale supported)
      Returns true if the pair of locales matches acceptably. This is influenced by Builder options such as setDirection(), setFavorSubtag(), and setMaxDistance().
      Parameters:
      desired - The desired locale.
      supported - The supported locale.
      Returns:
      true if the pair of locales matches acceptably.
    • match

      @Deprecated public double match(ULocale desired, ULocale desiredMax, ULocale supported, ULocale supportedMax)
      Deprecated.
      ICU 65 Build and use a matcher rather than comparing pairs of locales.
      Returns a fraction between 0 and 1, where 1 means that the languages are a perfect match, and 0 means that they are completely different.

      This is mostly an implementation detail, and the precise values may change over time. The implementation may use either the maximized forms or the others ones, or both. The implementation may or may not rely on the forms to be consistent with each other.

      Callers should construct and use a matcher rather than match pairs of locales directly.

      Parameters:
      desired - Desired locale.
      desiredMax - Maximized locale (using likely subtags).
      supported - Supported locale.
      supportedMax - Maximized locale (using likely subtags).
      Returns:
      value between 0 and 1, inclusive.
    • canonicalize

      public ULocale canonicalize(ULocale locale)
      Partially canonicalizes a locale (language). Note that for now, it is canonicalizing according to CLDR conventions (he vs iw, etc), since that is what is needed for likelySubtags.

      Currently, this is a much simpler canonicalization than what the ULocale class does: The language/script/region subtags are each mapped separately, ignoring the other subtags. If none of these change, then the input locale is returned. Otherwise a new ULocale with only those subtags is returned, removing variants and extensions.

      Parameters:
      locale - language/locale code
      Returns:
      ULocale with remapped subtags.
    • toString

      public String toString()
      Overrides:
      toString in class Object