Joda time: how to get dates on weekdays for a certain time interval?

Question

I have two LocalDates that represent a certain time interval. Now I have to get LocalDates of all Fridays that this interval contains. The easiest way to do this?

Answer 1

Solution: step lazily for one week.

import org.joda.time.LocalDate; import java.util.Iterator; public class DayOfWeekIterator implements Iterator<LocalDate>{ private final LocalDate end; private LocalDate nextDate; public DayOfWeekIterator(LocalDate start, LocalDate end, int dayOfWeekToIterate){ this.end = end; nextDate = start.withDayOfWeek(dayOfWeekToIterate); if (start.getDayOfWeek() > dayOfWeekToIterate) { nextDate = nextDate.plusWeeks(1); } } public boolean hasNext() { return !nextDate.isAfter(end); } public LocalDate next() { LocalDate result = nextDate; nextDate = nextDate.plusWeeks(1); return result; } public void remove() { throw new UnsupportedOperationException(); } } 

Test

 import org.joda.time.DateTimeConstants; import org.joda.time.LocalDate; public class DayOfWeekIteratorTest { public static void main(String[] args) { LocalDate startDate = new LocalDate(2010, 12, 1);//1st Dec 2010 LocalDate endDate = new LocalDate(2010, 12, 31);//31st Dec 2010 DayOfWeekIterator it = new DayOfWeekIterator(startDate, endDate, DateTimeConstants.FRIDAY); while (it.hasNext()) { System.out.println(it.next()); } } } 

Answer 2

 package org.life.java.so.questions; import org.joda.time.DateTime; import org.joda.time.DateTimeConstants; /** * * @author Jigar */ public class JodaTimeDateTraverseQuestion { public static void main(String[] args) { DateTime startDt = new DateTime(2010,12,1,0,0,0,0);//1st Dec 2010 DateTime endDt = new DateTime(2010,12,31,0,0,0,0);//31st Dec 2010 DateTime tempDate = new DateTime(startDt.getMillis()); while(tempDate.compareTo(endDt) <=0 ){ if(tempDate.getDayOfWeek() != DateTimeConstants.SATURDAY && tempDate.getDayOfWeek() != DateTimeConstants.SUNDAY){ System.out.println(""+tempDate); } tempDate = tempDate.plusDays(1); } } } 

Answer 3

TL; DR

 java.time.LocalDate.of( 2018 , Month.JANUARY , 23 ) // A date-only class in the modern *java.time* classes that supplant both Joda-Time and the troublesome old date-time classes. .with( TemporalAdjusters.next( DayOfWeek.FRIDAY ) // Nifty `TemporalAdjuster` implementation for moving to another date. Immutable Objects pattern means a new object is returned based on the original which remains unmodified. ) .isBefore( // Compare `LocalDate` objects with `isBefore`, `isAfter`, and `isEqual`. LocalDate.of( 2018 , Month.FEBRUARY , 27 ); ) 

java.time

FYI, the Joda-Time project is now in maintenance mode , and the team advises switching to the java.time classes.

Define your stop and run the LocalDate objects.

 LocalDate start = LocalDate.of( 2018 , Month.JANUARY , 23 ); LocalDate stop = LocalDate.of( 2018 , Month.FEBRUARY , 27 ); // TODO: Verify start.isBefore( stop ). 

Collect the Friday dates we find. You can optimize the collection setting a bit.

 // Pre-size the collection. int initialCapacity = ( int ) ( ChronoUnit.WEEKS.between( start , stop ) + 2 ); // Adding two for good measure. List < LocalDate > fridays = new ArrayList <>( initialCapacity ); 

Determine the first Friday using the start date, if it is Friday itself. Use the pair of TemporalAdjuster implementations proposed in the TemporalAdjusters class: next​(DayOfWeek) and nextOrSame​(DayOfWeek) . Pass the desired day of the week through the DayOfWeek enumeration, seven predefined objects, one for each day of the week from Monday to Sunday.

 LocalDate friday = start.with( TemporalAdjusters.nextOrSame( DayOfWeek.FRIDAY ) ); while ( friday.isBefore( stop ) ) { fridays.add( friday ); // Remember this Friday date. // Setup next loop. friday = friday.with( TemporalAdjusters.next( DayOfWeek.FRIDAY ) ); } System.out.println( "From " + start + " to " + stop + " = " + fridays ); 

From 2018-01-23 to 2018-02-27 = [2018-01-26, 2018-02-02, 2018-02-09, 2018-02-16, 2018-02-23]

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About java.time

The java.time framework is built into Java 8 and later. These classes supersede the nasty old legacy datetime classes such as java.util.Date , Calendar and SimpleDateFormat .

The Joda-Time project, now in maintenance mode , we recommend switching to the java.time classes.

To learn more, see the Oracle Tutorial . And search for qaru for many examples and explanations. JSR 310 specification .

You can exchange java.time objects directly with your database. Use a JDBC driver that conforms to JDBC 4.2 or later. No strings needed, no java.sql.* Classes needed.

Where to get java.time classes?

• Java SE 8 , Java SE 9 , and then
  • Built in.
  • Part of the standard Java API with integrated implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and Java SE 7
  • Most java.time functions return to Java 6 and 7 in ThreeTen-Backport .
• Android
  • Later versions of the Android package implementations of the java.time classes.
  • For earlier Android, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP ....

The ThreeTen-Extra project extends java.time with additional classes. This project is a proof of possible future additions to java.time. Here you can find useful classes such as Interval , YearWeek , YearQuarter and more .