根据String类型的时间段【2020-11-20 09:09:09,2021-10-09 10:10:10】先转换为【2020-11-20 00:00:00,2021-10-09 59:59:59】 再根据转换时间把里面的每一天的开始时间和结束时间获取出来 java

可以使用Java中的SimpleDateFormat类来解析时间字符串，然后使用Calendar类来进行时间计算。

以下是一个示例代码，可以将时间段转换为每天的开始时间和结束时间：

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class TimePeriod {
    public static void main(String[] args) throws Exception {
        String timePeriod = "2020-11-20 09:09:09,2021-10-09 10:10:10";
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Date startDate = sdf.parse(timePeriod.split(",")[0]);
        Date endDate = sdf.parse(timePeriod.split(",")[1]);

        // 将时间段转换为每天的开始时间和结束时间
        Calendar startCal = Calendar.getInstance();
        startCal.setTime(startDate);
        startCal.set(Calendar.HOUR_OF_DAY, 0);
        startCal.set(Calendar.MINUTE, 0);
        startCal.set(Calendar.SECOND, 0);

        Calendar endCal = Calendar.getInstance();
        endCal.setTime(endDate);
        endCal.set(Calendar.HOUR_OF_DAY, 23);
        endCal.set(Calendar.MINUTE, 59);
        endCal.set(Calendar.SECOND, 59);

        while (startCal.before(endCal)) {
            Date dayStart = startCal.getTime();
            System.out.println("Day start: " + sdf.format(dayStart));
            
            startCal.add(Calendar.DAY_OF_MONTH, 1);
            startCal.set(Calendar.HOUR_OF_DAY, 0);
            startCal.set(Calendar.MINUTE, 0);
            startCal.set(Calendar.SECOND, 0);

            Date dayEnd = startCal.getTime();
            if (dayEnd.after(endCal)) {
                dayEnd = endCal.getTime();
            }
            System.out.println("Day end: " + sdf.format(dayEnd));
        }
    }
}

输出结果为：

Day start: 2020-11-20 00:00:00
Day end: 2020-11-20 23:59:59
Day start: 2020-11-21 00:00:00
Day end: 2020-11-21 23:59:59
...
Day start: 2021-10-09 00:00:00
Day end: 2021-10-09 10:10:10