code: public static ULocale getFunctionalEquivalent(ULocale locale, boolean[] isAvailable) {
          return Factory.getDefaultFactory().getFunctionalEquivalent(locale, isAvailable);
      }
docs: Returns the 'functionally equivalent' locale with respect to
  plural rules.  Calling PluralRules.forLocale with the functionally equivalent
  locale, and with the provided locale, returns rules that behave the same.
  <br>
  All locales with the same functionally equivalent locale have
  plural rules that behave the same.  This is not exaustive;
  there may be other locales whose plural rules behave the same
  that do not have the same equivalent locale.
  
  @param locale the locale to check
  @param isAvailable if not null and of length &gt; 0, this will hold 'true' at
  index 0 if locale is directly defined (without fallback) as having plural rules
  @return the functionally-equivalent locale
  @hide draft / provisional / internal are hidden on Android