根据给定的频率将日期拆分为相等的间隔

Question

我正在尝试将一系列日期分成相等的间隔。这是我正在使用的代码。 （日期格式为 YYYY-MM-dd）

    Integer frequency= 4;
    Date startDate = '2020-02-27';
    Date endDate = '2022-02-26';
    String[] startD = string.valueOf(behadelPlan.Start_datum__c).split('-');
    String[] endD = string.valueOf(behadelPlan.Einddatum__c).split('-');

    //String[] dates;
    Integer x = 0;
    Integer startYear = Integer.valueof(startD[0]);
    Integer endYear = Integer.valueof(endD[0]);
    //while (x < 4) {
    for (Integer i = startYear; i <= endYear; i++) {
        Integer endMonth = i != endYear ? 11 : Integer.valueof(endD[1]) - 1;
        Integer startMon = i == startYear ? Integer.valueof(startD[1]) - 1 : 0;
        for (Integer j = startMon; j <= endMonth  && x < frequency; j = j + 1) {
            Integer month = j + 1;
            String displayMonth;
            if (month < 10) {
                displayMonth = '0' + month;
            } else {
                displayMonth = String.valueOf(month);
            }
            List<string> slist = new string[]{string.valueOf(i), displayMonth, '01'};
                string allstring = string.join(sList,'-');
           System.debug(slist);
            x+=1;
        }

    }

当我运行它时，我得到的输出为

2020-02-01
2020-03-01
2020-04-01
2020-05-01

在我的例子中，我想以相等的（每月一次，开始日期为一天）间隔生成日期。在上面的示例中，我应该以 4 个相等的间隔获得结果日期（因为我已经给出了几个月的频率）。

请告诉我如何实现这一目标。

这是一个简单的例子。

startdate = '2020-01-01'
endDate = '2020-12-01'
frequency = 4

输出应该是

2020-01-01
2020-03-01
2020-06-01
2020-09-01

Answer 1

我会这样做。我会为此给我们上课日历。

public class FrequencyTransform {

public static void main (String[] args) {
    System.out.println("Split a date into equal intervals based on a given frequency");
    Integer frequency= 4;
    try {
        Date startDate = new SimpleDateFormat("yyyy-mm-dd").parse("2020-02-27");
        Date endDate = new SimpleDateFormat("yyyy-mm-dd").parse("2021-02-26");

        Calendar startCalendar = Calendar.getInstance();
        startCalendar.clear();
        startCalendar.setTime(startDate);

        Calendar endCalendar = Calendar.getInstance();
        endCalendar.clear();
        endCalendar.setTime(endDate);

        // id you want the interval to be months
        int monthsElapsed = elapsed(startCalendar, endCalendar, Calendar.MONTH);
        System.out.println("Number of months between dates:" + monthsElapsed);
        int interval = monthsElapsed % frequency;
        System.out.println("For the frequency 4 the interval is: " + interval);

        while (!startCalendar.after(endCalendar)){
            startCalendar.add(Calendar.MONTH,interval);
            Date auxDate= startCalendar.getTime();
            System.out.println(auxDate);
        }
    }
    catch (ParseException ex) {
        ex.printStackTrace();

    }


}

private static int elapsed(Calendar before, Calendar after, int field) {

    Calendar clone = (Calendar) before.clone(); // Otherwise changes are been reflected.
    int elapsed = -1;
    while (!clone.after(after)) {
        clone.add(field, 1);
        elapsed++;
    }
    return elapsed;
}

}

这只是一个简单的例子。你可以从这里拿走。事情是日历允许您使用不同的时间单位。您可以使用 Calendar.DATE 代替 Calendar.MONTH 天，Calendar.YEAR 用于年份。不太确定你想如何进行拆分。

Answer 2

示例代码，

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class SOTest {

    static DateFormat dateFormat = new SimpleDateFormat("yyy-MM-dd");

    public static void main(String[] args) {
        try {
            String startDateString = "2020-01-01";
            String endDateString = "2020-12-01";

            int frequency = 4;
            Date startDate = (Date)dateFormat.parse(startDateString);
            Date endDate = (Date)dateFormat.parse(endDateString);
            Long intervalSize = (endDate.getTime()-startDate.getTime())/frequency;

            for(int i=0; i<= frequency && intervalSize > 0; i++) {
                Date date = new Date(startDate.getTime()+intervalSize*i);
                System.out.println("Date :: "+dateFormat.format(date));
            }
        } catch (ParseException e) {
            e.printStackTrace();
        }   
    }
}

上面的输出::

Date :: 2020-01-01
Date :: 2020-03-24
Date :: 2020-06-16
Date :: 2020-09-08
Date :: 2020-12-01

对于输入 :: startDate = '2020-02-27' , endDate = '2022-02-26', interval = 4

Date :: 2020-02-27
Date :: 2020-08-27
Date :: 2021-02-26
Date :: 2021-08-27
Date :: 2022-02-26