JDK8: unable to parse LocalTime

问题

I managed to parse a String to a LocalDate object:

DateTimeFormatter f1=DateTimeFormatter.ofPattern("dd MM yyyy");
LocalDate d=LocalDate.parse("26 08 1984",f1);
System.out.println(d); //prints "1984-08-26"

But I cannot do the same with LocalTime. This piece of code:

DateTimeFormatter f2=DateTimeFormatter.ofPattern("hh mm");
LocalTime t=LocalTime.parse("11 08",f2); //exception here
System.out.println(t);

Throws a DateTimeParseException:

Exception in thread "main" java.time.format.DateTimeParseException: Text '11 08' could not be parsed: Unable to obtain LocalTime from TemporalAccessor: {MinuteOfHour=8, HourOfAmPm=11},ISO of type java.time.format.Parsed
    at java.time.format.DateTimeFormatter.createError(Unknown Source)
    at java.time.format.DateTimeFormatter.parse(Unknown Source)
    at java.time.LocalTime.parse(Unknown Source)
    at com.mui.cert.Main.<init>(Main.java:21)
    at com.mui.cert.Main.main(Main.java:12)
Caused by: java.time.DateTimeException: Unable to obtain LocalTime from TemporalAccessor: {MinuteOfHour=8, HourOfAmPm=11},ISO of type java.time.format.Parsed
    at java.time.LocalTime.from(Unknown Source)
    at java.time.LocalTime$$Lambda$15/1854731462.queryFrom(Unknown Source)
    at java.time.format.Parsed.query(Unknown Source)
    ... 4 more

What am I doing wrong?

回答1:

If you use a specific format, according to API:

The string must represent a valid time and is parsed using DateTimeFormatter.ISO_LOCAL_TIME.

hh mm

for 24h must be

HH mm

or for 12h

kk mm

The handled formats must have this conditions:

Two digits for the hour-of-day. This is pre-padded by zero to ensure two digits.
A colon
Two digits for the minute-of-hour. This is pre-padded by zero to ensure two digits.
If the second-of-minute is not available then the format is complete.
A colon
Two digits for the second-of-minute. This is pre-padded by zero to ensure two digits.
If the nano-of-second is zero or not available then the format is complete.
A decimal point
One to nine digits for the nano-of-second. As many digits will be output as required.

回答2:

Use DateTimeFormatter.ofPattern("kk mm"); for 12 hour clock or DateTimeFormatter.ofPattern("HH mm") for 24 hour clock

If you want to parse time with hh you must combine it wih a where you define AM or PM:

DateTimeFormatter f2 = DateTimeFormatter.ofPattern("hh mm a");
LocalTime t = LocalTime.parse("11 08 AM", f2);

回答3:

In this case Unable to obtain LocalTime from TemporalAccessor means it cannot determine the how far through the day the given string represents i.e. there is not enough information to construct a LocalTime. Behind the scenes, the code looks something like this expanded Java 8 version (which gives a similar error):

DateTimeFormatter f2 = DateTimeFormatter.ofPattern("hh mm");
TemporalAccessor temporalAccessor = f2.parse("11 08");
LocalTime t = temporalAccessor.query(LocalTime::from);
System.out.println(t);

The LocalTime::from documentation says

The conversion uses the TemporalQueries.localTime() query, which relies on extracting the NANO_OF_DAY field.

Your error is telling you that the TemporalAccessor only has two fields, neither of which is a NANO_OF_DAY field. The minimum allowable patterns for retrieving a LocalTime using a DateTimeFormatter are:

DateTimeFormatter.ofPattern("ha");
DateTimeFormatter.ofPattern("Ka");
DateTimeFormatter.ofPattern("ah");
DateTimeFormatter.ofPattern("aK");
DateTimeFormatter.ofPattern("k");
DateTimeFormatter.ofPattern("H");

Your pattern must contain at least one of those strings to get a NANO_OF_DAY field in the internal TemporalAccessor from which a LocalTime can be constructed.

回答4:

You need to use capital HH in the pattern

DateTimeFormatter f2=DateTimeFormatter.ofPattern("HH mm");

or do this, for clock-hour-of-am-pm you need to specify it.

This should also work

DateTimeFormatter f2=DateTimeFormatter.ofPattern("hh mm a");
LocalTime t=LocalTime.parse("11 08 AM",f2); //exception here

来源：https://stackoverflow.com/questions/30754259/jdk8-unable-to-parse-localtime

标签

java

java-8

date-parsing