在java中给定LocalDate后，如何获得下周五13号？

Question

我有一个任务的问题。我必须得到下周五13日，因为给定的日期使用LocalDate。

你们有什么想法吗？

Answer 1

您可以使用IntStream迭代几天：

public static LocalDate findFridayThirteen(LocalDate fromDate) {
    return IntStream.iterate(0, i -> i + 1)
            .mapToObj(fromDate::plusDays)
            .filter(date -> date.getDayOfWeek() == DayOfWeek.FRIDAY 
                    && date.getDayOfMonth() == 13)
            .findFirst()
            .orElseThrow();
}

测试：

LocalDate date = LocalDate.of(2022, 1, 1);

LocalDate friday13 = findFridayThirteen(date);

DateTimeFormatter formatter = DateTimeFormatter.ofLocalizedDate(FormatStyle.FULL);

System.out.println(friday13.format(formatter));

输出：

Friday, May 13, 2022

Answer 2

    public static void main(String[] args) {
    boolean is13Friday = false;
    LocalDate nextFriday = LocalDate.now();
    while (!is13Friday) {
        nextFriday = getNextFriday(nextFriday);
        is13Friday = is13Friday(nextFriday);
    }
    System.out.println(nextFriday);

}

public static LocalDate getNextFriday(LocalDate d) {
    return d.with(TemporalAdjusters.next(DayOfWeek.FRIDAY));
}

public static boolean is13Friday(LocalDate d) {
    return d.getDayOfMonth() == 13;
}

Answer 3

只需在LocalDate中添加7天，即可获得预期的日期：

例如：

 LocalDate today = LocalDate.now();

 //tomorrow
 LocalDate tomorrow = today.plusDays(1);

 // next week day
 LocalDate nextWeekDay= today.plusDays(7);

或者通过这个得到它：

today.with(TemporalAdjusters.next(DayOfWeek.FRIDAY));