java - 获取两个日期之间的完整 "monday to sunday"周

Question

这个问题已经有答案了:

Get the number of weeks between two Dates. (19 个回答)

已关闭 8 年前。

看看你能不能帮我。我想获取两个日期 d1 和 d2 之间的周数(从星期一开始到星期日结束)。假设 d2 早于 d1。这部分代码已经编程并可以运行。我现在的问题是我无法正确编写周程序。这就是我现在所做的:

public static void getFullWeeks(Calendar d1, Calendar d2){
    int Weeks = 0;
    Calendar date2 = d2;
    Calendar addWeek = GregorianCalendar.getInstance();
    addWeek.setTime(date2.getTime());
    addWeek.add(Calendar.DATE, 6);

    while(addWeek.before(d1) || addWeek.equals(d1)){
        if(date2.get(Calendar.DAY_OF_WEEK) == Calendar.MONDAY){
            Weeks++;
        }
        date2.add(Calendar.DATE,1);
    }

    System.out.println(
        "The number of weeks (from monday to sunday) between both dates are: " 
        + Weeks);
}

但是输出是“0 周”，因此程序无法运行。怎么了？我没有遇到该错误，并且无法找到该问题的有效解决方案。

谢谢!!

Answer 1

在没有外部库的 Java 8 中，您可以执行如下操作:

*编辑以说明从周一开始的一周

// TechTrip - ASSUMPTION d1 is earlier than d2
// leave that for exercise
public static long getFullWeeks(Calendar d1, Calendar d2){
    // In Java the week starts on Sunday from an integral perspective
    //  public final static int SUNDAY = 1;
    // SEQUENTIAL UP TO
    // public final static int SATURDAY = 7;

    // make the starting date relative to the Monday we need to calculate from
    int dayOfStartWeek = d1.get(Calendar.DAY_OF_WEEK);

    // IF we have a partial week we should add an offset that moves the start
    // date UP TO the next Monday to simulate a week starting on Monday
    // eliminating partial weeks from the calculation
    // NOTE THIS METHOD WILL RETURN NEGATIVES IF D1 < D2 after adjusting for 
    // offset
    if (dayOfStartWeek == Calendar.SUNDAY) {
        // add an offset of 1 day because this is a partial week
        d1.add(Calendar.DAY_OF_WEEK, 1);
    } else if (dayOfStartWeek != Calendar.MONDAY){
        // add an offset for the partial week
        // Hence subtract from 9 accounting for shift by 1
        // and start at 1
        // ex if WEDNESDAY we need to add 9-4 (WED Int Val) = 5 days
        d1.add(Calendar.DAY_OF_WEEK, 9 - dayOfStartWeek);
    }

    Instant d1i = Instant.ofEpochMilli(d1.getTimeInMillis());
    Instant d2i = Instant.ofEpochMilli(d2.getTimeInMillis());

    LocalDateTime startDate = LocalDateTime.ofInstant(d1i, ZoneId.systemDefault());
    LocalDateTime endDate = LocalDateTime.ofInstant(d2i, ZoneId.systemDefault());

    return ChronoUnit.WEEKS.between(startDate, endDate);
}

主要内容如下:

public static void main(String[] args) {
    Calendar d1 = Calendar.getInstance();
    Calendar d2 = Calendar.getInstance();
    d2.add(Calendar.WEEK_OF_YEAR, 6);
    System.out.println(
            "The number of weeks (from monday to sunday) between both dates are: " 
            + getFullWeeks(d1, d2));
}

如果开始日期是星期一，则输出如下:

两个日期之间的周数(从星期一到星期日)为:6

注意，我没有将日期 d2 分配给 d1，使其成为相同的引用。在这种情况下，您将得到 0。

*ChronoUnit 采用 Temporal，它只是日期、时间或偏移量。它们必须是同一类型。时间可以用加号和减号来操纵。