Question

我正在尝试在日历中更改DayofWeek，但似乎没有像我期望的那样工作。这是一个例子。我将日历时间设置为星期五时间，但是当我将Calendar.DAY_OF_WEEK设置为Calendar.SUNDAY时，它将向下移动到下周。由于Calendar.SUNDAY是默认的第一天，不应该将时间移回当周的开头吗？

import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.TimeZone;

public class GenericWeekdayOpenFunction implements TimePeriodFunction {

    public static void main(String[] args) {
        // Nov 8 is Friday
        long time = DateUtilities.newDateTimeAsMillis(2013, 11, 8, 10, 00, 00);
        System.out.println(DateUtilities.formatGmtDatetime(time));

        Calendar calendar = new GregorianCalendar(TimeZone.getTimeZone("GMT"));
        calendar.setTimeInMillis(time);

        // move day of week to Sunday, expect date to be Nov 3
        calendar.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
        System.out.println(DateUtilities.formatGmtDatetime(calendar.getTimeInMillis()));    // wrong

        // move day of week to Friday, expect date to be Nov 8
        calendar.set(Calendar.DAY_OF_WEEK, Calendar.FRIDAY);
        System.out.println(DateUtilities.formatGmtDatetime(calendar.getTimeInMillis()));
    }

}

输出：

08-11-2013 10:00:00.000
10-11-2013 10:00:00.000
08-11-2013 10:00:00.000

Answer 1

您的方案在基本Calendar类使用情况下正常工作：

Calendar c = new GregorianCalendar(TimeZone.getTimeZone("GMT"));
Date d = new Date(113, 10, 8, 10, 0, 0);
c.setTimeInMillis(d.getTime());
System.out.println(c.getTime());
c.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
System.out.println(c.getTime());
c.set(Calendar.DAY_OF_WEEK, Calendar.FRIDAY);
System.out.println(c.getTime());

输出：

Fri Nov 08 10:00:00 IST 2013

Sun Nov 03 10:00:00 IST 2013

Fri Nov 08 10:00:00 IST 2013

请注意，Date(113, 10, 8, 10, 0, 0);仅用于快速检查，但已弃用。尝试任何其他组合也可以正常工作。您可以尝试使用基本Calendar API和打印日期，即

Calendar c = new GregorianCalendar(TimeZone.getTimeZone("GMT"));
System.out.println(c.getTime());//current day
c.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
System.out.println(c.getTime());

第二个日期应该回到之前的星期日而不是即将到来的日期。如果它适合您，那么DateUtilities实施可能会令人怀疑。

Answer 2

我认为方法set(int field, int value) 工作接近最近的一天（而不是同一周的DAY_OF_WEEK）。但您可以使用add(int field, int amount)函数add(Calendar.DATE, -5)来执行此操作。

如何在java.util.Calendar中更改DAY_OF_WEEK？

2 个答案: