I wish to remove the Joda-Time library from my project.
I am trying to convert a two digit year to full year. The following code from Joda-Time can fulfil the purpos
java.time
doesn’t supply default values for month and day of month the way it seems that Joda-Time does. The message says that it cannot obtain a LocalDate
from a year alone, or conversely, it is missing month and day (you may supply your own default values, though, as demonstrated in Mikhail Kholodkov’s answer). Generally this behaviour is here to help us: it reminds us to supply all the values needed, and makes it clear from the code if any default values are used, and which.
Just use the Year
class of java.time
. First declare
public static final DateTimeFormatter TWO_YEAR_FORMATTER = new DateTimeFormatterBuilder()
.appendValueReduced(ChronoField.YEAR, 2, 2, 1950)
.toFormatter();
Then use
int year = Year.parse("99", TWO_YEAR_FORMATTER).getValue();
System.out.println(year);
Output
1999
Insert your desired base value where I put 1950 to specify a year within 99 years (inclusive) from that year. If you want the year to be in the past including this year, you may use:
private static final Year base = Year.now(ZoneId.of("Asia/Kolkata")).minusYears(99);
public static final DateTimeFormatter TWO_YEAR_FORMATTER = new DateTimeFormatterBuilder()
.appendValueReduced(ChronoField.YEAR, 2, 2, base.getValue())
.toFormatter();
BTW, don’t take my word for it, but I think Joda-Time uses current year minus 30 years as base or pivot. If this is so, using 30 instead of 99 in the last snippet will be the most compatible (so will also give you the 1999 you expected).
You need to provide default values for DAY_OF_MONTH
and MONTH_OF_YEAR
DateTimeFormatter TWO_YEAR_FORMATTER = new DateTimeFormatterBuilder()
.appendPattern("yy")
.parseDefaulting(ChronoField.MONTH_OF_YEAR, 1)
.parseDefaulting(ChronoField.DAY_OF_MONTH, 1)
.toFormatter();
In addition,
Java-8 uses the range 2000-2099 per default, not like SimpleDateFormat the range -80 years until +20 years relative to today.
Full answer
Since you're parsing years only, in order to have '99' as '1999' your code should be like this:
DateTimeFormatter TWO_YEAR_FORMATTER = new DateTimeFormatterBuilder()
.appendPattern("")
.parseDefaulting(ChronoField.MONTH_OF_YEAR, 1)
.parseDefaulting(ChronoField.DAY_OF_MONTH, 1)
.appendValueReduced(ChronoField.YEAR_OF_ERA, 2, 2, LocalDate.now().minusYears(80))
.toFormatter();
You could parse the year directly using formatter.parse(input, Year::from)
:
import java.time.*;
import java.time.format.*;
class Main {
public static void main(String[] args) {
DateTimeFormatter TWO_YEAR_FORMATTER = DateTimeFormatter.ofPattern("yy");
Year year = TWO_YEAR_FORMATTER.parse("99", Year::from);
System.out.println(year);
}
}
Note that this will output 2099
. To output 1999, you should use a specific formatter like the one suggested by Ole V.V. in their answer.
You can't create a LocalDate
because the String
you give doesn't provide the information needed to fill all required fields.
You can create a Year
though
Year parsed = Year.parse("99", TWO_YEAR_FORMATTER);
int year = parsed.getValue();
The problem is that you can't parse a year on its own into a LocalDate. A LocalDate needs more information than that.
You can use the parse
method of the formatter, which will give you a TemporalAccessor, and then get the year field from that:
int year = TWO_YEAR_FORMATTER.parse("99").get(ChronoField.YEAR);
System.out.println(year);
Addressing the discrepancy between the two: these are two distinct APIs. Yes, they are very similar, and the java.time
package was informed by design decisions of JodaTime, but it was never intended to be a drop-in replacement for it.
See this answer if you would like to change the pivot year (by default '99' will resolve to 2099 and not 1999).