Parse date-time from String with offset with one-digit hours

I need to parse date in Java. I have String value 2018-05-15 09:32:51.550082 +3:00 and I need to parse it into date-time. I tried to parse to ZonedDateTime, but I got an error at index 10. Tried to parse with DateTimeFormatter parser ‘yyyy-MM-dd HH:mm:ss.SSSSSS Z’ and got error at index 26. Apparently my UTC offset of +3:00 cannot be parsed. How can I do this?

Answer

Java 9 and later allows:

    String dateTimeString = "2018-05-15 09:32:51.550082 +3:00";
    DateTimeFormatter formatter = new DateTimeFormatterBuilder()
            .appendPattern("uuuu-MM-dd HH:mm:ss.SSSSSS ")
            .appendOffset("+H:MM:ss", "+0:00")
            .toFormatter();
    OffsetDateTime dateTime = OffsetDateTime.parse(dateTimeString, formatter);
    System.out.println(dateTime);

Output:

2018-05-15T09:32:51.550082+03:00

For Java 8 or the ThreeTen Backport you will probably have to prepare your date-time string before parsing it:

    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss.SSSSSS XXX");
    dateTimeString 
            = dateTimeString.replaceFirst("([+-])(\d(?::\d\d){0,2})$", "$10$2");

The rest is as before and gives the same result. The replaceFirst call inserts a 0 between the + and 3:00, but only if the hours were only one digit. The regular expression is hard to read, so you will prefer the Java 9 solution.

As already discussed in the comments the hard part is the offset of +3:00. Java’s built-in formatters and the format pattern letters you can use for specifying your own format all require two-digit hours in the offset. The DateTimeFormatterBuilder.appendOffset method that I am using allows a limited number of formats to be specified; 9 different formats in Java 8; 22 in Java 9. Link: Documentation of appendOffset().