java - Java cron中问号的意义

Question

来源维基百科:

Question mark (?) is used instead of '*' for leaving either day-of-month or day-of-week blank.

上述说法对我来说没有多大意义。

所以如果我写一些 cron 作为 0 0 0 ？ * * 那么它是指每个月的第一天还是意味着它将每天执行？

这有点令人困惑，因为 Java crons 以秒开头，而其他 crons 以分钟开头。

Answer 1

根据Quartz CronTrigger tutorial (Quartz 被 www.cronmaker.com 使用，如上所引用)，? 通配符仅用于月日和星期几字段:

? ("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.

我猜 * 在这里不合适，因为 * 意味着在一周中的每一天执行，这与它应该只在 10 日运行的规则相矛盾月份。