根据时间段【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

可以通过Java中的日期时间类 `LocalDate` 和 `LocalDateTime` 来实现该功能。

首先，我们需要将时间段转换为 `LocalDateTime` 对象，然后将时间部分设置为 00:00:00 或 23:59:59，最后遍历每一天，获取每一天的开始时间和结束时间。

以下是代码示例：

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.format.DateTimeFormatter;

public class TimeUtils {

    public static void main(String[] args) {
        String startStr = "2020-11-20 09:09:09";
        String endStr = "2021-10-09 10:10:10";
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        LocalDateTime start = LocalDateTime.parse(startStr, formatter);
        LocalDateTime end = LocalDateTime.parse(endStr, formatter);
        // 将时间部分设置为 00:00:00 或 23:59:59
        LocalDateTime startOfDay = start.with(LocalTime.MIN);
        LocalDateTime endOfDay = end.with(LocalTime.MAX);

        // 遍历每一天，获取每一天的开始时间和结束时间
        LocalDate startDate = startOfDay.toLocalDate();
        LocalDate endDate = endOfDay.toLocalDate();
        while (!startDate.isAfter(endDate)) {
            LocalDateTime startOfDayOfDate = startDate.atStartOfDay();
            LocalDateTime endOfDayOfDate = startDate.atTime(LocalTime.MAX);
            System.out.println("Start time of " + startDate + ": " + startOfDayOfDate);
            System.out.println("End time of " + startDate + ": " + endOfDayOfDate);
            startDate = startDate.plusDays(1);
        }
    }

}

输出结果如下：

Start time of 2020-11-20: 2020-11-20T00:00
End time of 2020-11-20: 2020-11-20T23:59:59.999999999
Start time of 2020-11-21: 2020-11-21T00:00
End time of 2020-11-21: 2020-11-21T23:59:59.999999999
...
Start time of 2021-10-09: 2021-10-09T00:00
End time of 2021-10-09: 2021-10-09T23:59:59.999999999