code: protected Collator guessCollator() {
          ULocale collLocale = getAvailableLocale(TYPE_COLLATOR);
          if (collLocale == null) {
              collLocale = ULocale.ROOT;
          }
          return Collator.getInstance(collLocale);
      }
docs: This function can be overridden by subclasses to use different heuristics.
  <b>It MUST return a 'safe' value,
  one whose modification will not affect this object.</b>
  
  @hide draft / provisional / internal are hidden on Android