No matter what the intermediate LocalDate value is, setting its dayOfWeek property to Monday always rounds "down" such that adding six days to the beginning of the month gives you the first Monday.

不管中间 LocalDate 值是多少，将其 dayOfWeek 属性设置为 Monday 总是能够四舍五入，这样的话，在每月的开始再加上 6 天就能够让您得到第一个星期一。

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