public static String getHost(String address) {
        Matcher matcher = HOST_PORT_PATTERN.matcher(address);
        return matcher.matches() ? matcher.group(1) : null;
    }
Extracts the hostname from a "host:port" address string.
@param address address string to parse
@return hostname or null if the given address is incorrect
clients/src/main/java/org/apache/kafka/common/utils/Utils.java