class CronUtils {

    public static String getCronExpression( String seconds, String minutes, String hours, String days, String months,
        String weekday )
    {
        return String.join( " ",
            (seconds == null ? "*" : seconds),
            (minutes == null ? "*" : minutes),
            (hours == null ? "*" : hours),
            (days == null ? "*" : days),
            (months == null ? "*" : months),
            (weekday == null ? "*" : weekday)
        );
    }

}