DateTimeFormatter to parse string with both Zone offset and timezone-CodePudding

This question might sound similar to most of the other questions asked here on Stackoverflow but I could not figure out my problem. I want to parse the string value into a date.

String dateTime = "23 Oct 2020 02:44:58 1000"

The solution to this problem is:

DateTimeFormatterBuilder builder = new DateTimeFormatterBuilder();
builder.parseCaseInsensitive();
builder.appendPattern("d MMM yyyy HH:mm[:ss] Z");
DateTimeFormatter dtf = builder.toFormatter();

ZonedDateTime zonedDateTime = ZonedDateTime.parse(dateTime, dtf);
Instant instant = zonedDateTime.toInstant();
Date finalDate = Date.from(instant);

If I want to parse the date with timezone instead like String dateTime = "23 Oct 2020 02:44:58 AEST" then I need to change the builder.appendPattern("d MMM yyyy HH:mm[:ss] Z"); from capital Z to small z as mentioned here.

The question here is how would I make my parser flexible enough for it to handle either timezone or offset value?

Note. I have used [ss] as the seconds' field is optional. And as per documentation using VV was similar to z while 'V' did not work for me.

CodePudding user response：

You can add them as optional parts to the formatter, just like you did with the seconds part:

DateTimeFormatter formatter = new DateTimeFormatterBuilder()
    .parseCaseInsensitive()
    .appendPattern("d MMM yyyy HH:mm[:ss] [Z][z]")
    .toFormatter(Locale.ROOT);

Online demo

[ and ] denote an optional part: the corresponding text is consumed if it can be successfully parsed by means of the pattern within the brackets, otherwise, no text is consumed and the pattern within is skipped.

CodePudding user response：

You can try using try-catch block

DateTimeFormatterBuilder builder = new DateTimeFormatterBuilder(); 
builder.parseCaseInsensitive(); 
builder.appendPattern("d MMM yyyy HH:mm[:ss] Z"); 
DateTimeFormatter dtf = builder.toFormatter();

DateTimeFormatterBuilder builder = new DateTimeFormatterBuilder(); 
builder.parseCaseInsensitive(); 
builder.appendPattern("d MMM yyyy HH:mm[:ss] z"); 
DateTimeFormatter dtf = builder.toFormatter();

ZonedDateTime zonedDateTime;
try {
    zonedDateTime = ZonedDateTime.parse(dateTime, dtf1);
} catch (DateTimeParseException e) {
    zonedDateTime = ZonedDateTime.parse(dateTime, dtf2);
}
Instant instant = zonedDateTime.toInstant();
Date finalDate = Date.from(instant);