问题
I am trying to parse: 2014-05-02-10.45.05.993280-5:00 where the -5:00 is the offset from UTC. Using a java.time DateTimeFormatter in Java 8.
For the first bit I have the following: yyyy-MM-dd-HH.mm.ss.SSSSSS however, I can't figure out what the pattern should be to parse the offset also.
If I had the offset with 4 digits (-05:00) I could use: yyyy-MM-dd-HH.mm.ss.SSSSSSxxx, but this doesn't work for 3 digits.
Any ideas?
回答1:
Use capital letter X instead of x, hence XXX. The difference is that big X can recognize the input letter "Z" as UTC-Offset +00:00 while small pattern letter X cannot.
Suggested pattern:
yyyy-MM-dd-HH.mm.ss.SSSSSSXXX
Please be also aware of following JDK-bug:
java.time.format.DateTimeFormatter cannot parse an offset with single digit hour
UPDATE:
I have now tested the described workaround in the bug-log.
String input = "2014-05-02-10.45.05.993280-5:00";
DateTimeFormatter f = new DateTimeFormatterBuilder().appendPattern("yyyy-MM-dd-HH.mm.ss.SSSSSS").parseLenient().appendOffset("+HH:MM", "Z").toFormatter();
System.out.println(f.parse(input, ZonedDateTime::from));
But it throws an exception:
Exception in thread "main" java.time.format.DateTimeParseException: Text '2014-05-02-10.45.05.993280-5:00' could not be parsed at index 26 at java.time.format.DateTimeFormatter.parseResolved0(DateTimeFormatter.java:1947) at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1849) at HelloWorld.main(HelloWorld.java:16)
So lenient parsing does not help either. So there are now only three options left for you:
Use workaround suggested by bug reporter: [...] workaround is to parse the date/time separately, use a hand coded parser for the offset and combine the LocalDateTime with the hand parsed offset. Not an easy work around.
Try your own specialized string preprocessing. If you have a fixed format then you can try to insert the zero-digit at position 26 (if the total input length is one digit too small).
Or you use an external library which can do this. My library Time4J (v4.0) can do that if you are willing to add an extra dependency. See this code:
String input = "2014-05-02-10.45.05.993280-5:00";
ZonalDateTime zdt =
ZonalDateTime.parse(
input,
Moment.localFormatter("yyyy-MM-dd-HH.mm.ss.SSSSSSXXX", PatternType.CLDR));
System.out.println(zdt); // 2014-05-02T10:45:05,993280UTC-05:00
ZonedDateTime result = zdt.toTemporalAccessor();
Update: According to JDK-bug-status, the bug has been fixed for Java-9, but a backport for Java-8 does not seem to be available though.
回答2:
Offset for SimpleDateFormat sign is Z check Java7 or Java8 SimpleDateFormat API.
Then, your parser format for String
2014-05-02-10.45.05.993280-5:00
must be:
yyyy-MM-dd-HH.mm.ss.SSSSSSZ
UPDATE: for DateTimeFormatter the offset Patterns for Formatting and Parsing are:
O localized zone-offset offset-O GMT+8; GMT+08:00; UTC-08:00;
X zone-offset 'Z' for zero offset-X Z; -08; -0830; -08:30; -083015; -08:30:15;
x zone-offset offset-x +0000; -08; -0830; -08:30; -083015; -08:30:15;
Z zone-offset offset-Z +0000; -0800; -08:00;
Your desired pattern in DateTimeFormatter is X.
回答3:
All the answers are good. The java8+ have these patterns for parsing and formatting timezone: V, z, O, X, x, Z.
Here's they are, for parsing, according to rules from the documentation :
Symbol Meaning Presentation Examples
------ ------- ------------ -------
V time-zone ID zone-id America/Los_Angeles; Z; -08:30
z time-zone name zone-name Pacific Standard Time; PST
O localized zone-offset offset-O GMT+8; GMT+08:00; UTC-08:00;
X zone-offset 'Z' for zero offset-X Z; -08; -0830; -08:30; -083015; -08:30:15;
x zone-offset offset-x +0000; -08; -0830; -08:30; -083015; -08:30:15;
Z zone-offset offset-Z +0000; -0800; -08:00;
But how about formatting?
Here's a sample for a date (assuming ZonedDateTime) that show these patters behavior for different formatting patters:
// The helper function:
static void printInPattern(ZonedDateTime dt, String pattern) {
System.out.println(pattern + ": " + dt.format(DateTimeFormatter.ofPattern(pattern)));
}
// The date:
String strDate = "2020-11-03 16:40:44 America/Los_Angeles";
DateTimeFormatter format = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss zzzz");
ZonedDateTime dt = ZonedDateTime.parse(strDate, format);
// 2020-11-03T16:40:44-08:00[America/Los_Angeles]
// Rules:
// printInPattern(dt, "V"); // exception!
printInPattern(dt, "VV"); // America/Los_Angeles
// printInPattern(dt, "VVV"); // exception!
// printInPattern(dt, "VVVV"); // exception!
printInPattern(dt, "z"); // PST
printInPattern(dt, "zz"); // PST
printInPattern(dt, "zzz"); // PST
printInPattern(dt, "zzzz"); // Pacific Standard Time
printInPattern(dt, "O"); // GMT-8
// printInPattern(dt, "OO"); // exception!
// printInPattern(dt, "OO0"); // exception!
printInPattern(dt, "OOOO"); // GMT-08:00
printInPattern(dt, "X"); // -08
printInPattern(dt, "XX"); // -0800
printInPattern(dt, "XXX"); // -08:00
printInPattern(dt, "XXXX"); // -0800
printInPattern(dt, "XXXXX"); // -08:00
printInPattern(dt, "x"); // -08
printInPattern(dt, "xx"); // -0800
printInPattern(dt, "xxx"); // -08:00
printInPattern(dt, "xxxx"); // -0800
printInPattern(dt, "xxxxx"); // -08:00
printInPattern(dt, "Z"); // -0800
printInPattern(dt, "ZZ"); // -0800
printInPattern(dt, "ZZZ"); // -0800
printInPattern(dt, "ZZZZ"); // GMT-08:00
printInPattern(dt, "ZZZZZ"); // -08:00
In the case of positive offset the + sign character is used everywhere(where there is - now) and never omitted.
This well works for new java.time types. If you're about to use these for java.util.Date or java.util.Calendar - not all going to work as those types are broken(and so marked as deprecated, please don't use them)
来源：https://stackoverflow.com/questions/30710829/java-time-datetimeformatter-pattern-for-timezone-offset