class ConfigObserver {

    public ConfigObserver onDurationValue(String key, Duration defaultValue, ConfigValueListener<Duration> listener) {
        return onSingleConfigValue(key, Duration::parse, defaultValue, listener);
    }

    public  ConfigObserver(String applicationName);
    public  ConfigObserver(File configDirectory, String applicationName);
    public  ConfigObserver(File configDirectory, String applicationName, List<String> profiles);
    public  ConfigObserver(ConfigLoader configLoader);

}