code: public static E164CountryCode lookup(String address) {
          // analyze just the first few chars -- max of 4 or length of address
          int len = (address.length() > maxPrefixLength ? maxPrefixLength : address.length());
          // search backwards first, return the first result
          for (int i = len; i > 0; i--) {
              String prefix = address.substring(0, i);
              E164CountryCode entry = byPrefix.get(prefix);
              if (entry != null) {
                  return entry;
              }
          }
          // nothing found
          return null;
      }
docs: Looks up an E164CountryCode object by analyzing the address and returning
  the best match.  For example, 12125551212 will return an entry for the US.
  @param address The address to lookup.
  @return