How to convert a Instant to a LocalTime?

问题

I'm not really understanding Temporal Adjusters or Java's new time library even after reading numerous tutorials.

How would I convert an Instant object to a LocalTime object. I was thinking something along the lines of the following:

LocalTime time = LocalTime.of(
        instantStart.get(ChronoField.HOUR_OF_DAY),
        instantStart.get(ChronoField.MINUTE_OF_HOUR)
    );

But it isn't working. How would I do this?

回答1:

The way I understand it... Instant is a UTC style time, agnostic of zone always UTC. LocaleTime is time at a given zone. So you'd expect the following would work given that Instant implements TemporalAccessor,

Instant instant = Instant.now();
LocalTime local =  LocalTime.from(instant);

but you get "Unable to obtain LocalTime from TemporalAccessor" error. Instead you need to state where "local" is. There is no default - probably a good thing.

Instant instant = Instant.now();
LocalTime local =  LocalTime.from(instant.atZone(ZoneId.of("GMT+3")));
System.out.println(String.format("%s => %s", instant, local));

Output

2014-12-07T07:52:43.900Z => 10:52:43.900

instantStart.get(ChronoField.HOUR_OF_DAY) throws an error because it does not conceptually support it, you can only access HOUR_OF_DAY etc. via a LocalTime instance.

来源：https://stackoverflow.com/questions/27340650/how-to-convert-a-instant-to-a-localtime