Difference between * and ? in Spring @Scheduled(cron=".....")

The tutorial is outdated. The symbol ? means exactly the same than *. As of Spring 3.1.2.RELEASE, the call hierarchy is:

The constructor CronTrigger(String) calls the constructor CronSequenceGenerator(String) which calls parse(String) which calls setDays(BitSet bits, String field, int max). Its implementation is clear:

private void setDays(BitSet bits, String field, int max) {
    if (field.contains("?")) {
        field = "*";
    }
    setNumberHits(bits, field, 0, max);
}

So, if ?, then *.

asterix stands for all possible values. question marks should be used for non specific value

*("all values") - used to select all values within a field. For example, "" in the minute field means *"every minute".

? ("no specific value") - useful when you need to specify something in one of the two fields in which the character is allowed, but not the other. For example, if I want my trigger to fire on a particular day of the month (say, the 10th), but don't care what day of the week that happens to be, I would put "10" in the day-of-month field, and "?" in the day-of-week field. See the examples below for clarification.

Copied from the tutorial