时间：如何获得下周五？

Question

如何使用 Joda-Time API获取下周五。

今天的 LocalDate 是today。在我看来，你必须在本周五之前或之后决定你是谁。请参阅此方法：

private LocalDate calcNextFriday(LocalDate d) {
    LocalDate friday = d.dayOfWeek().setCopy(5);
    if (d.isBefore(friday)) {
        return d.dayOfWeek().setCopy(5);
    } else {
        return d.plusWeeks(1).dayOfWeek().setCopy(5);
    }
}

是否可以缩短或使用oneliner？

PS：请不要建议我使用JDK的日期/时间。 Joda-Time是一个更好的API。

Java 8引入了 java.time 包（教程）哪个更好。

Answer 1

java.time

使用Java内置的 java.time 框架8及更高版本（教程）您可以使用 TemporalAdjusters 获取下一页或 previous 星期几-。

private LocalDate calcNextFriday(LocalDate d) {
  return d.with(TemporalAdjusters.next(DayOfWeek.FRIDAY));
}

Answer 2

可以以更容易阅读的方式进行：

if (d.getDayOfWeek() < DateTimeConstants.FRIDAY) {
    return d.withDayOfWeek(DateTimeConstants.FRIDAY));
} else if (d.getDayOfWeek() == DateTimeConstants.FRIDAY) {
    // almost useless branch, could be merged with the one above
    return d;
} else {
    return d.plusWeeks(1).withDayOfWeek(DateTimeConstants.FRIDAY));
}

或缩写为

private LocalDate calcNextFriday(LocalDate d) {    
    if (d.getDayOfWeek() < DateTimeConstants.FRIDAY) {
        d = d.withDayOfWeek(DateTimeConstants.FRIDAY));
    } else {
        d = d.plusWeeks(1).withDayOfWeek(DateTimeConstants.FRIDAY));
    }    
    return d; // note that there's a possibility original object is returned
}

甚至更短

private LocalDate calcNextFriday(LocalDate d) {
    if (d.getDayOfWeek() >= DateTimeConstants.FRIDAY) {
        d = d.plusWeeks(1);
    }
    return d.withDayOfWeek(DateTimeConstants.FRIDAY);
}

PS。我没有测试实际代码！ ：）

Answer 3

您的代码在一行

private LocalDate calcNextFriday3(LocalDate d) {
    return d.isBefore(d.dayOfWeek().setCopy(5))?d.dayOfWeek().setCopy(5):d.plusWeeks(1).dayOfWeek().setCopy(5);
}

替代方法

private LocalDate calcNextDay(LocalDate d, int weekday) {
    return (d.getDayOfWeek() < weekday)?d.withDayOfWeek(weekday):d.plusWeeks(1).withDayOfWeek(weekday);
}


private LocalDate calcNextFriday2(LocalDate d) {
    return calcNextDay(d,DateTimeConstants.FRIDAY);
}

有点测试过; - ）

Answer 4

我只是浪费了30分钟试图自己解决这个问题，但我需要一直向前推进。

无论如何，这是我的解决方案：

public static DateTime rollForwardWith(ReadableInstant now, AbstractPartial lp) {
    DateTime dt = lp.toDateTime(now);
    while (dt.isBefore(now)) {
        dt = dt.withFieldAdded(lp.getFieldTypes()[0].getRangeDurationType(), 1);
    }
    return dt;
}

现在您只需要为星期几制作一个Partial（LocalDate）。

Partial().with(DateTimeFieldType.dayOfWeek(), DateTimeConstants.FRIDAY); 

现在，如果当前日期在（现在）之后，那么部分最重要的字段将是+1。

如果您在2012年3月部分参与，它将创建2013年3月的新日期时间或<！> lt;。

Answer 5

import java.util.Calendar;

private Calendar getNextweekOfDay(int weekOfDay) {
    Calendar today = Calendar.getInstance();
    int dayOfWeek = today.get(Calendar.DAY_OF_WEEK);
    int daysUntilNextWeekOfDay = weekOfDay - dayOfWeek;
    if (daysUntilNextWeekOfDay == 0) daysUntilNextWeekOfDay = 7;
    Calendar nextWeekOfDay = (Calendar)today.clone();
    nextWeekOfDay.add(Calendar.DAY_OF_WEEK, daysUntilNextWeekOfDay);
    return nextWeekOfDay;
}

// set alarm for next Friday 9am
public void setAlarm() {
    Calendar calAlarm = getNextweekOfDay(Calendar.FRIDAY);
    calAlarm.set(Calendar.HOUR_OF_DAY, 9);//9am
    calAlarm.set(Calendar.MINUTE, 0);
    calAlarm.set(Calendar.SECOND, 0);
    scheduleAlarm(calAlarm);// this is my own method to schedule a pendingIntent
}

Answer 6

计算字节@fvu的答案可以进一步缩短为：

private LocalDate calcNextFriday(LocalDate d) {
  return d.plusWeeks(d.getDayOfWeek() < DateTimeConstants.FRIDAY ? 0 : 1).withDayOfWeek(DateTimeConstants.FRIDAY);
}

Answer 7

一个简单的基于模数的解决方案，如果不允许将java版本升级到java8或以后，或者使用标准的java日期库作为jodatime

，它应该适用于大多数以前的java版本。

添加到您的日期的天数由以下公式给出：

（7 + Calendar.FRIDAY - yourDateAsCalendar.get（Calendar.DAY_OF_WEEK））％7

另请注意，通过将静态字段Calendar.FRIDAY更改为您的给定工作日，可以对任何工作日进行推广。

下面的一些代码段

public static void main(String[] args) {
    for (int i = 0; i < 15; i++) {

        Calendar cur = Calendar.getInstance();
        cur.add(Calendar.DAY_OF_MONTH, i);

        Calendar friday = Calendar.getInstance();
        friday.setTime(cur.getTime());
        friday.add(Calendar.DAY_OF_MONTH, (7 + Calendar.FRIDAY - cur.get(Calendar.DAY_OF_WEEK)) % 7);

        System.out.println(MessageFormat.format("Date {0} -> {1} ", cur.getTime(),  friday.getTime()));
    }
}