code: private static final void addLocaleIDsFromIndexBundle(String baseName,
              ClassLoader root, Set<String> locales) {
          ICUResourceBundle bundle;
          try {
              bundle = (ICUResourceBundle) UResourceBundle.instantiateBundle(baseName, ICU_RESOURCE_INDEX, root, true);
              bundle = (ICUResourceBundle) bundle.get(INSTALLED_LOCALES);
          } catch (MissingResourceException e) {
              if (DEBUG) {
                  System.out.println("couldn't find " + baseName + '/' + ICU_RESOURCE_INDEX + ".res");
                  Thread.dumpStack();
              }
              return;
          }
          UResourceBundleIterator iter = bundle.getIterator();
          iter.reset();
          while (iter.hasNext()) {
              String locstr = iter.next(). getKey();
              locales.add(locstr);
          }
      }
docs: and returns the data in a different form.