code: public static String getRegion(String tzid) {
          String region = REGION_CACHE.get(tzid);
          if (region == null) {
              int zoneIdx = getZoneIndex(tzid);
              if (zoneIdx >= 0) {
                  try {
                      UResourceBundle top = UResourceBundle.getBundleInstance(
                              ICUData.ICU_BASE_NAME, ZONEINFORESNAME, ICUResourceBundle.ICU_DATA_CLASS_LOADER);
                      UResourceBundle regions = top.get(kREGIONS);
                      if (zoneIdx < regions.getSize()) {
                          region = regions.getString(zoneIdx);
                      }
                  } catch (MissingResourceException e) {
                      // throw away
                  }
                  if (region != null) {
                      REGION_CACHE.put(tzid, region);
                  }
              }
          }
          return region;
      }
docs: Return the region code for this tzid.
  If tzid is not a system zone ID, this method returns null.