java如何将LocalDateTime转换回Instant，而不知道时区，而是使用时钟？

Question

我能。在进行了一些操作之后，比如添加时间单位，我想将其转换为Instant。但它需要时区。如何得到它

Clock clock = Clock.fixed(...);
LocalDateTime localDateTime = LocalDateTime.now(clock);
localDateTime = localDateTime.plusMinutes(60);
return localDateTime.toInstant(clock.getZone().getRules().getOffeset(...I need instant I don't have yet!...)

Answer 1

您可以传递区域偏移量，例如ZoneOffset.UTC到^{}。或者，您可以使用^{}创建ZonedDateTime，并将其转换为Instant

import java.time.Clock;
import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZoneOffset;

public class Main {
    public static void main(String[] args) {
        Clock clock = Clock.systemUTC();

        LocalDateTime localDateTime = LocalDateTime.now(clock);
        localDateTime = localDateTime.plusMinutes(60);

        // UTC
        Instant instant = localDateTime.toInstant(ZoneOffset.UTC);
        System.out.println(instant);

        // A custom zone offset
        instant = localDateTime.toInstant(ZoneOffset.of("+02:00"));
        System.out.println(instant);

        // Your JVM's default timezone
        instant = localDateTime.atZone(ZoneId.systemDefault()).toInstant();
        System.out.println(instant);

        // A specific timezone
        instant = localDateTime.atZone(ZoneId.of("Africa/Ceuta")).toInstant();
        System.out.println(instant);
    }
}

输出：

2021-03-10T14:30:35.294134Z
2021-03-10T12:30:35.294134Z
2021-03-10T14:30:35.294134Z
2021-03-10T13:30:35.294134Z

从Trail: Date Time了解有关现代日期时间API的更多信息

Answer 2

据我所知，当您想要转换回Instant时，您仍然可以访问Clock。你可以很容易地从时钟上得到时区。然后转换如下：

    Clock clock = Clock.fixed(Instant.EPOCH, ZoneId.of("Pacific/Tahiti"));
    LocalDateTime localDateTime = LocalDateTime.now(clock);
    localDateTime = localDateTime.plusMinutes(60);
    Instant convertedBack = localDateTime.atZone(clock.getZone()).toInstant();
    
    System.out.println(convertedBack);

此示例代码段的输出为：

1970-01-01T01:00:00Z