java周切分，按照指定weekday为一周的开始

最新推荐文章于 2022-07-08 20:27:33 发布

Esther_lee

最新推荐文章于 2022-07-08 20:27:33 发布

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分类专栏： Java

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本文介绍如何在Java中实现自定义周概念，以周六为一周的开始，详细阐述了从输入日期计算周号的过程，包括处理跨年情况，并提供了相应代码示例。

目标：扩充周的概念为周六到周五、周四到周三。也即认为一周的开始是周六而不是java默认的周末

输入：start_date，end_date

输出：XX年XX周

首先，周切分

以周六到周五为例，先拿到start_date所在的年份的第一个周六FirstSaturday作为第一周，将start_date向后拨到第一个周六，然后计算start_date与FirstSaturday之间相差了多少天，在整除7即可知道start_date所在的周六是本年的第几周。

end_date的处理与start_date类似，需要注意跨年的情况，将end_date向前拨到第一个周五。

对于FirstSaturday的计算时，注意，不仅要调整年、月、日，还要调整时、分、秒。如果不调整时、分、秒，那么计算出来的FirstSaturday的时分秒将会是当前的时分秒，在计算start_date与FirstSaturday之间相差多少天时，由于采用的是时间戳相减，而时间上不到24小时就会认为不是一天，就会带来误差。具体例子可以看：http://www.cnblogs.com/0201zcr/p/5000977.html

所以FirstSaturday的计算如下：

FirstSaturday = Calendar.getInstance();
FirstSaturday.set(startCal.get(Calendar.YEAR), Calendar.JANUARY, 1, 0, 0, 0);//重要！！！
while (FirstSaturday.get(Calendar.DAY_OF_WEEK) != Calendar.SATURDAY) {
       FirstSaturday.add(Calendar.DAY_OF_YEAR, 1);
}

注意跨年的情况。当跨年时，我们需要重新计算FirstSaturday。这里只需要将年份重新变更，比如2015跨2016时，之前FirstSaturday是2015年的第一个周六，那么跨年时，将FirstSaturday改成2016年的第一个周六即可。

具体代码如下：

//计算开始日期是第几周
long beginWeekNum = (startCal.getTimeInMillis() / 1000 - FistSaturday.getTimeInMillis() / 1000) / SevenDay + 1;
String beginWeek = String.valueOf(beginWeekNum);
if (beginWeekNum < 10) {
   beginWeek = "0" + beginWeekNum;
}
//计算结束日期是第几周
FistSaturday = Calendar.getInstance();
FistSaturday.set(endCal.get(Calendar.YEAR), Calendar.JANUARY, 1, 0, 0, 0);
while (FistSaturday.get(Calendar.DAY_OF_WEEK) != Calendar.SATURDAY) {
     FistSaturday.add(Calendar.DAY_OF_YEAR, 1);
}
long endWeekNum = (endCal.getTimeInMillis() / 1000 - FistSaturday.getTimeInMillis() / 1000) / SevenDay + 1;
String endWeek = String.valueOf(endWeekNum);
if (endWeekNum < 10) {
    endWeek = "0" + endWeekNum;
}

对于需要计算某段时间内具体每周的周号、每周的开始时间和结束时间的代码，如下：

import java.text.SimpleDateFormat;
import java.util.*;

/**
 *
 * @author zhaoruixing
 */
public class WeekHelper {

    private static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    private static long SevenDay = 604800;

    /**
     * @param startDate
     * @param endDate
     * @param args the command line arguments
     * @return
     */
    public static List<Week> getWeekSplit(Date startDate, Date endDate) {
        ArrayList<Week> WeekList = new ArrayList<>();
        Calendar startCal = Calendar.getInstance();
        startCal.setTime(startDate);
        Calendar endCal = Calendar.getInstance();
        endCal.setTime(endDate);

        Calendar FistSaturday = Calendar.getInstance();
        FistSaturday.set(startCal.get(Calendar.YEAR), Calendar.JANUARY, 1, 0, 0, 0);
        while (FistSaturday.get(Calendar.DAY_OF_WEEK) != Calendar.SATURDAY) {
            FistSaturday.add(Calendar.DAY_OF_YEAR, 1);
        }

        while (startCal.get(Calendar.DAY_OF_WEEK) != Calendar.SATURDAY) {
            startCal.add(Calendar.DAY_OF_YEAR, 1);
        }
        while (endCal.get(Calendar.DAY_OF_WEEK) != Calendar.FRIDAY) {
            endCal.add(Calendar.DAY_OF_YEAR, -1);
        }
        System.out.println(sdf.format(startCal.getTime()) + "\t" + sdf.format(endCal.getTime()));
        int startYear = startCal.get(Calendar.YEAR);
        while (startCal.compareTo(endCal) < 0) {
            int endYear = startCal.get(Calendar.YEAR);
            if (startYear < endYear) {
                FistSaturday.set(endYear, Calendar.JANUARY, 1, 0, 0, 0);
                while (FistSaturday.get(Calendar.DAY_OF_WEEK) != Calendar.SATURDAY) {
                    FistSaturday.add(Calendar.DAY_OF_YEAR, 1);
                }
                startYear = endYear;
            }
            Week everyWeek = new Week();
            long WeekNum = (startCal.getTimeInMillis() / 1000 - FistSaturday.getTimeInMillis() / 1000) / SevenDay + 1;
            String WeekNumStr = String.valueOf(WeekNum);
            if (WeekNum < 10) {
                WeekNumStr = "0" + WeekNum;
            }
            everyWeek.setYear(startCal.get(Calendar.YEAR));
            everyWeek.setWeekBegin(sdf.format(startCal.getTime()));
            startCal.add(Calendar.DATE, 6);
            everyWeek.setWeekEnd(sdf.format(startCal.getTime()));
            everyWeek.setWeekNum(WeekNumStr);
            startCal.add(Calendar.DATE, 1);
            WeekList.add(everyWeek);
        }
        Iterator<Week> iter = WeekList.iterator();
        System.out.println("开始打印");
        while (iter.hasNext()) {
            Week everyweek = iter.next();
            System.out.println(everyweek.getYear() + "年第" + everyweek.getWeekNum() + "周\t" + "开始时间：" + everyweek.getWeekBegin() + "\t结束时间" + everyweek.getWeekEnd());
        }
        return WeekList;
    }

    public static void main(String[] args) {
        String start = "2015-12-12";
        String end = "2016-02-01";
        try {
            Date startDate = sdf.parse(start);
            Date endDate = sdf.parse(end);
            getWeekSplit(startDate, endDate);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

class Week {

    String weekNum;
    int year;
    String weekBegin;
    String weekEnd;

    public String getWeekNum() {
        return weekNum;
    }

    public void setWeekNum(String weekNum) {
        this.weekNum = weekNum;
    }

    public int getYear() {
        return year;
    }

    public void setYear(int year) {
        this.year = year;
    }

    public String getWeekBegin() {
        return weekBegin;
    }

    public void setWeekBegin(String weekBegin) {
        this.weekBegin = weekBegin;
    }

    public String getWeekEnd() {
        return weekEnd;
    }

    public void setWeekEnd(String weekEnd) {
        this.weekEnd = weekEnd;
    }
}

执行结果如下：