code: public static String resolveIpAddress(String hostname) throws UnknownHostException {
      Preconditions.checkNotNull(hostname, "hostname");
      Preconditions.checkArgument(!hostname.isEmpty(),
              "Cannot resolve IP address for empty hostname");
      return InetAddress.getByName(hostname).getHostAddress();
    }
docs: Resolves a given hostname IP address.
  
  @param hostname the input hostname, which could be an alias
  @return the hostname IP address
  @throws UnknownHostException if the given hostname cannot be resolved