tl;dr
Year year = Year.of ( 2012 ) ; // Represent an entire year.
year
.atDay( 1 ) // Determine the first day of the year. Returns a `LocalDate` object.
.datesUntil( // Generates a `Stream<LocalDate>`.
year
.plusYears( 1 ) // Returns a new `Year` object, leaving the original unaltered.
.atDay( 1 ) // Returns a `LocalDate`.
) // Returns a `Stream<LocalDate>`.
.forEach( // Like a `for` loop, running through each object in the stream.
System.out :: println // Each `LocalDate` object in stream is passed to a call of `System.out.println`.
)
;
java.time
The other Answers are outmoded as of Java 8.
The old date-time classes bundled with earlier versions of Java have been supplanted with the java.time framework built into Java 8 and later. See Tutorial.
LocalDate (date-only)
If you care only about the date without the time-of-day, use the LocalDate class. The LocalDate class represents a date-only value, without time-of-day and without time zone.
LocalDate start = LocalDate.of( 2016 , 1 , 1 ) ;
LocalDate stop = LocalDate.of( 2016 , 1 , 23 ) ;
To get the current date, specify a time zone. For any given moment, today’s date varies by time zone. For example, a new day dawns earlier in Paris than in Montréal.
LocalDate today = LocalDate.now( ZoneId.of( "America/Montreal" ) );
We can use the isEqual, isBefore, and isAfter methods to compare. In date-time work we commonly use the Half-Open approach where the beginning of a span of time is inclusive while the ending is exclusive.
List<LocalDate> localDates = new ArrayList<>();
LocalDate localDate = start;
while ( localDate.isBefore( stop ) ) {
localDates.add( localDate );
// Set up the next loop.
localDate = localDate.plusDays( 1 );
}
LocalDate::datesUntil
You can obtain a stream of LocalDate objects.
Stream< LocalDate > dates = start.datesUntil( stop ) ;
dates.forEach( System.out::println ) ;
LocalDateRange
If doing much of this work, add the ThreeTen-Extra library to your project. This gives you the LocalDateRange class to represent your pair of start and stop LocalDate objects.
Instant (date-time)
If you have old java.util.Date objects, which represent both a date and a time, convert to the Instant class. An Instant is a moment on the timeline in UTC.
Instant startInstant = juDate_Start.toInstant();
Instant stopInstant = juDate_Stop.toInstant();
From those Instant objects, get LocalDate objects by:
- Applying the time zone that makes sense for your context to get
ZonedDateTime object. This object is the very same moment on the timeline as the Instant but with a specific time zone assigned.
- Convert the
ZonedDateTime to a LocalDate.
We must apply a time zone as a date only has meaning within the context of a time zone. As we said above, for any given moment the date varies around the world.
Example code.
ZoneId zoneId = ZoneId.of( "America/Montreal" );
LocalDate start = ZonedDateTime.ofInstant( startInstant , zoneId ).toLocalDate();
LocalDate stop = ZonedDateTime.ofInstant( stopInstant , zoneId ).toLocalDate();
