code: public static String getShortID(TimeZone tz) {
          String canonicalID = null;
  
          if (tz instanceof OlsonTimeZone) {
              canonicalID = ((OlsonTimeZone)tz).getCanonicalID();
          }
          else {
              canonicalID = getCanonicalCLDRID(tz.getID());
          }
          if (canonicalID == null) {
              return null;
          }
          return getShortIDFromCanonical(canonicalID);
      }
docs: Returns the time zone's short ID for the zone.
  For example, "uslax" for zone "America/Los_Angeles".
  @param tz the time zone
  @return the short ID of the time zone, or null if the short ID is not available.