使用Java 8计算两个日期之间的天数，同时忽略一周中的某些天

Question

下面我有3种方法。第一个很简单。它只计算总天数。但是，第二个不仅会计算天数，还会忽略传递给方法的星期几。

我的问题是第三种方法并不总是正确的。它应该匹配第二种方法。我猜它与闰年有关，因为当它不正确时差异通常为+ = 3 | 4。

其他信息

我试图以某种方式模仿Excel weekday(serial_number,[return_type])公式。

serial_number = startDate:Date - daysOfWeekToInclude:Array<Integer>

实施例

  | A       | B                                                  | C
  +---------+----------------------------------------------------+-----------
1 | Start   | =DATE(2014,9,7)                                    | 9/7/2014                 
2 | End     | =DATE(2025,6,13)                                   | 6/13/2025                    
3 | Include | ={1,2,4,6} (Mon, Tue, Thu, & Sat)                  | <Disp Only>
4 | Days    | =SUM(INT((WEEKDAY($B$1-{1,2,4,6},1)+$B$2-$B$1)/7)) | 2248 

此处有关于此功能的更多信息：How to count / calculate the number of days between two dates in Excel?

原始图像

方法

1. 只需计算两个日期之间的天数。

   public static int simpleDaysBetween(final LocalDate start,
           final LocalDate end) {
       return (int) ChronoUnit.DAYS.between(start, end);
   }
   

2. 使用循环计算天数，忽略一周中的某些天。

   public static int betterDaysBetween(final LocalDate start,
           final LocalDate end, final List<DayOfWeek> ignore) {
       int count = 0;
       LocalDate curr = start.plusDays(0);
   
       while (curr.isBefore(end)) {
           if (!ignore.contains(curr.getDayOfWeek())) {
               count++;
           }
           curr = curr.plusDays(1); // Increment by a day.
       }
   
       return count;
   }
   

3. 计算天数。再次但没有循环。

   public static int bestDaysBetween(final LocalDate start,
           final LocalDate end, final List<DayOfWeek> ignore) {
       int days = simpleDaysBetween(start, end);
   
       if (days == 0) {
           return 0;
       }
   
       if (!ignore.isEmpty()) {
           int weeks = days / 7;
           int startDay = start.getDayOfWeek().getValue();
           int endDay = end.getDayOfWeek().getValue();
           int diff = weeks * ignore.size();
   
           for (DayOfWeek day : ignore) {
               int currDay = day.getValue();
               if (startDay <= currDay) {
                   diff++;
               }
               if (endDay > currDay) {
                   diff++;
               }
           }
   
           if (endDay > startDay) {
               diff -= endDay - startDay;
           }
   
           return days - diff;
       }
   
       return days;
   }
   

完整代码

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.temporal.ChronoUnit;
import java.util.Arrays;
import java.util.List;

public class DayCounter {
    public static void main(String[] args) {
        final LocalDate start = LocalDate.of(2014, 9, 7);
        final LocalDate end = LocalDate.of(2025, 6, 13);
        List<DayOfWeek> ignore = Arrays.asList(DayOfWeek.SUNDAY, DayOfWeek.WEDNESDAY, DayOfWeek.FRIDAY);

        print(start);
        print(end);

        System.out.println(simpleDaysBetween(start, end));
        System.out.println(betterDaysBetween(start, end, ignore));
        System.out.println(bestDaysBetween(start, end, ignore));
    }

    public static void print(LocalDate date) {
        System.out.printf("%s -> %s%n", date, date.getDayOfWeek());
    }

    public static int simpleDaysBetween(final LocalDate start,
            final LocalDate end) {
        return (int) ChronoUnit.DAYS.between(start, end);
    }

    public static int betterDaysBetween(final LocalDate start,
            final LocalDate end, final List<DayOfWeek> ignore) {
        int count = 0;
        LocalDate curr = start.plusDays(0);

        while (curr.isBefore(end)) {
            if (!ignore.contains(curr.getDayOfWeek())) {
                count++;
            }
            curr = curr.plusDays(1); // Increment by a day.
        }

        return count;
    }

    public static int bestDaysBetween(final LocalDate start,
            final LocalDate end, final List<DayOfWeek> ignore) {
        int days = simpleDaysBetween(start, end);

        if (days == 0) {
            return 0;
        }

        if (!ignore.isEmpty()) {
            int weeks = days / 7;
            int startDay = start.getDayOfWeek().getValue();
            int endDay = end.getDayOfWeek().getValue();
            int diff = weeks * ignore.size();

            for (DayOfWeek day : ignore) {
                int currDay = day.getValue();
                if (startDay <= currDay) {
                    diff++;
                }
                if (endDay > currDay) {
                    diff++;
                }
            }

            if (endDay > startDay) {
                diff -= endDay - startDay;
            }

            return days - diff;
        }

        return days;
    }
}

Answer 1

如果我们谈论Java 8 API，为什么不使用Java 8功能......

static long daysBetween(LocalDate start, LocalDate end, List<DayOfWeek> ignore) {
    return Stream.iterate(start, d->d.plusDays(1))
                 .limit(start.until(end, ChronoUnit.DAYS))
                 .filter(d->!ignore.contains(d.getDayOfWeek()))
                 .count();
}

Answer 2

您使用的是错误的Excel公式。请参阅＆＃34;使用SUM和INT功能来计算工作日数＆＃34;您提供的网站。它将公式表述为：

=SUM(INT((WEEKDAY(A2-{2,3,4,5,6})+B2-A2)/7))

在Excel中，星期日是1，星期六是7.花括号内的数字表示要包括的星期几。因此，对于您的情况，公式将是：

=SUM(INT((WEEKDAY(A2-{2,3,5,7})+B2-A2)/7))

请参阅随附的屏幕截图：

以下代码返回时返回2247：

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.Month;
import java.time.Year;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;


public class SO25798876 {

    public static void main(String[] args) {
        String strStartDate = "09/07/2014";
        String strEndDate = "06/13/2025";
        String pattern = "MM/dd/yyyy";
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern(pattern);
        LocalDate startDate = LocalDate.parse(strStartDate, formatter);
        LocalDate endDate = LocalDate.parse(strEndDate, formatter);

        int count = 0;

        while(startDate.isBefore(endDate) || startDate.isEqual(endDate)) {  // you may want to not to use the isEqual method        
            DayOfWeek dayOfWeek = startDate.getDayOfWeek();         

            if(!(dayOfWeek == DayOfWeek.SUNDAY || dayOfWeek == DayOfWeek.WEDNESDAY || dayOfWeek == DayOfWeek.FRIDAY)) {
                count++;
            }           

            startDate = startDate.plusDays(1);
        }

        System.out.println(count);  
    }
}

如果添加以下代码，您还提到了java.time可能没有考虑闰年的疑问，这是错误的

long year = startDate.getYear();

if(Year.isLeap(year)) {
    Month month = startDate.getMonth();

    if(month == Month.FEBRUARY && startDate.getDayOfMonth() == 29) {
        System.out.println("Calculated 29th Feb for the year: " + year);
    }
}

你会看到它正在打印：

Calculated 29th Feb for the year: 2016
Calculated 29th Feb for the year: 2020
Calculated 29th Feb for the year: 2024

最后，计数将为2247，与Excel结果相符。

快乐的编码。

-Tapas