如何在下午4点和凌晨2点之间的两个时间生成随机时间？

html5 • • 问答

我试过使用 -

int startSeconds = restaurant.openingTime.toSecondOfDay();
int endSeconds = restaurant.closingTime.toSecondOfDay();
LocalTime timeBetweenOpenClose = LocalTime.ofSecondOfDay(ThreadLocalRandom.current().nextInt(startSeconds, endSeconds));

但这通常会遇到错误，如 nextInt(origin, bounds), origin 不能小于 bounds，如果 myopeningTime是 16:00:00 和closingTime02:00:00 ，则会发生这种情况。

回答

您可以添加一天的秒数 ( 24*60*60) 当startSeconds大于时endSeconds表示第二天的秒数，并在获得随机数以一天的秒数取模后，通过有效的秒值将其转换为 LocalTime。

int secondsInDay = (int)Duration.ofDays(1).getSeconds();
if(startSeconds > endSeconds){
  endSeconds += secondsInDay;
}
LocalTime timeBetweenOpenClose = LocalTime.ofSecondOfDay(
              ThreadLocalRandom.current().nextInt(startSeconds, endSeconds) % secondsInDay);

回答

如果不应用日期和时区，我们无法知道从下午 4 点到凌晨 2 点之间将经过多长时间。因此，我们将使用 解决它ZonedDateTime。

  1. 第一步将是：ZonedDateTime通过调用获取LocalDate#atStartOfDay
ZoneId zoneId = ZoneId.systemDefault();
LocalDate.now().atStartOfDay(zoneId);
  1. 接下来，使用ZonedDateTime#with获取ZonedDateTime具有指定时间的 a。
  2. 现在，您可以Instant从ZonedDateTimeusing派生ZonedDateTime#toInstant。
  3. 一旦以Instant这种方式导出start 和 end s，就可以使用ThreadLocalRandom.current().nextLong生成longstart 和 end Instants范围内的值，并使用获得的值来获取所需的Instant.
  4. 最后，您可以ZonedDateTime从这个Instantusing派生 a Instant#atZone，然后使用获得所需的时间ZonedDateTime#toLocalTime。

演示：

import java.time.Instant;
import java.time.LocalDate;
import java.time.LocalTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.util.concurrent.ThreadLocalRandom;

public class Main {
    public static void main(String[] args) {
        // Change it as per the applicable timezone e.g. ZoneId.of("Europe/London")
        ZoneId zoneId = ZoneId.systemDefault();
        LocalDate today = LocalDate.now();
        
        ZonedDateTime zdtStart = today.atStartOfDay(zoneId)
                                      .with(LocalTime.of(16, 0));
        
        ZonedDateTime zdtEnd = today.plusDays(1)
                                    .atStartOfDay(zoneId)
                                    .with(LocalTime.of(2, 0));
        
        ZonedDateTime zdtResult = 
                Instant.ofEpochMilli(
                            ThreadLocalRandom
                            .current()
                            .nextLong(
                                        zdtStart.toInstant().toEpochMilli(), 
                                        zdtEnd.toInstant().toEpochMilli()
                                    )
                        ).atZone(zoneId);
        
        LocalTime time = zdtResult.toLocalTime();
        System.out.println(time);
    }
}

从Trail: Date Time 中了解有关现代日期时间 API 的更多信息。

ONLINE DEMO 随机打印 100 次。

  • @VaibhavAgrawal A `ZonedDateTime` is a date and time in a time zone. If you want the time for a particular day and it needs to work correctly in all time zones, then you need this because it takes DST transitions and other time line anomalies into account. An `Instant` is a plain point in time (as the name says). The code converts from `LocalTime` to `ZonedDateTime` to `Instant` to milliseconds in order to do the math on the milliseconds values, then converts back to `Instant` to `ZonedDateTime` to `LocalTime`.
  • That's neat @OleV.V. I am getting it now..Thanks!!
    And the issue of _origin less than bounds_ gets solved because EpochMilli returns the number of milliseconds from the epoch of _1970-01-01T00:00:00Z_.
    Although 4 PM and 2 AM were just examples so rather than hardcoding values `LocalTime.of(16, 0)` instead `restaurant.openingTime` can be used. And `ZonedDateTime zdtEnd = today.plusDays(1).atStartOfDay(zoneId).with(LocalTime.of(2, 0));` can be checked using if condition so that if closingTime falls within same day i.e. `if (openingTime.isBefore(closingTime))` then `plusDays(1)` can be removed.
以上是如何在下午4点和凌晨2点之间的两个时间生成随机时间？的全部内容。
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