How to parse case-insensitive strings with JSR-310 DateTimeFormatter?

Question

JSR-310 has a handy class DateTimeFormatter which allows you to construct a DateTimeFormatter. I particularly like the pattern(String) method - see javadoc

However, I hit a problem whereby this is case sensitive -- e.g.

DateTimeFormatters.pattern("dd-MMM-yyyy");

matches with "01-Jan-2012", but not with "01-JAN-2012" or "01-jan-2012".

One approach would be to break the string down and parse components, or another would be to use Regex to replace the case-insensitive strings with the case-sensitive string.

But it feels like there ought to be an easier way...

Worm

Answer 1

And there is... according to the User Guide (offline, see JavaDoc instead), you should use DateTimeFormatterBuilder to build a complex DateTimeFormatter

e.g.

DateTimeFormatterBuilder builder = new DateTimeFormatterBuilder();
builder.parseCaseInsensitive();
builder.appendPattern("dd-MMM-yyyy");
DateTimeFormatter dateFormat = builder.toFormatter();

Worm

Slightly neater third line: builder.appendPattern("dd-MMM-yyyy"); – Mousey

Slightly neater: most of the times, a builder provides methods returning the builder, so you can use method chaining: new DateTimeFormatterBuilder().parseCaseInsensitive().appendPattern.... – Abduction

Further improvement: Never use SimpleDateFormat or DateTimeFormatter without a Locale. Use .toFormatter(Locale.ENGLISH) in this case. – Turbellarian

Answer 2

This alternative is usefull for initializating static variables:

DateTimeFormatter myFormatter = new DateTimeFormatterBuilder()
                               .parseCaseInsensitive()
                               .appendPattern("dd-MMM-yyyy")
                               .toFormatter(Locale.ENGLISH);

Elum

Seems to duplicate the accepted Answer from a couple years earlier – Regenerative

Answer 3

Just an extra Note, the order matters.

This is case insensitive:

            DateTimeFormatter format = new DateTimeFormatterBuilder()
                .parseCaseInsensitive()
                .parseLenient()
                .appendPattern("HH:mm EEEE")
                .toFormatter(); 

This is not:

            DateTimeFormatter format = new DateTimeFormatterBuilder()
                .appendPattern("HH:mm EEEE")
                .parseCaseInsensitive()
                .parseLenient()
                .toFormatter(); 

Bacterin

Good point! Further improvement: Never use SimpleDateFormat or DateTimeFormatter without a Locale. Use .toFormatter(Locale.ENGLISH) in this case. – Turbellarian