Generating all days between 2 given dates in Java [duplicate]

Question

I'm trying to get an array of Dates, while my input is a 'from'/'to' structure. So my input is:

String date1 = "2014-01-01";
String date2 = "2014-05-01";

My output should be an Arraylist with all dates between date1 and date2. I've already looked for this, but I could only find questions about the difference between 2 dates:

SimpleDateFormat myFormat = new SimpleDateFormat("dd MM yyyy");
String inputString1 = "23 01 1997";
String inputString2 = "27 04 1997";

try {
    Date date1 = myFormat.parse(inputString1);
    Date date2 = myFormat.parse(inputString2);
    long diff = date2.getTime() - date1.getTime();
    System.out.println ("Days: " + TimeUnit.DAYS.convert(diff,TimeUnit.MILLISECONDS));
} catch (ParseException e) {
e.printStackTrace();
}

Any hints or suggestions? All other questions are for iOS or SQL.

Answer 1

Take a look at JodaTime: http://joda-time.sourceforge.net/apidocs/org/joda/time/DateTime.html

DateTime dateTime1 = new DateTime(date1);
DateTime dateTime2 = new DateTime(date2);

List<Date> allDates = new ArrayList();

while( dateTime1.before(dateTime2) ){
   allDates.add( dateTime1.toDate() );
   dateTime1 = dateTime1.plusDays(1);
}

Answer 2

Below is the code to get array of dates between the two string date.

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.List;
public class DateFormatExample {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        SimpleDateFormat myFormat = new SimpleDateFormat("yyyy-MM-dd");
        SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");  
        String date1 = "2014-01-01";
        String date2 = "2014-05-01";
        try {
            Date d1 = myFormat.parse(date1);
            Date d2 = myFormat.parse(date2);
            List<Date> allDates = new ArrayList<Date>();
            List<String> allDatesString = new ArrayList<String>();
            while( d1.before(d2) ){
                d1 = addDays(d1, 1);  
                allDates.add(d1);
                allDatesString.add(formatter.format(d1));
            }
            System.out.println(allDates);
            System.out.println(allDatesString);
        } catch (ParseException e) {
        e.printStackTrace();
        }
    }
    private static Date addDays(Date d1, int i) {
        GregorianCalendar cal = new GregorianCalendar();
        cal.setTime(d1);
        cal.add(Calendar.DATE, 1);
        return cal.getTime();
    }

}

Answer 3

If you don't want to use third party libraries you can use Calendar:

Check here a working demo.

public static void main(String[] args) throws Exception {
    SimpleDateFormat myFormat = new SimpleDateFormat("dd MM yyyy");
    String inputString1 = "23 01 1997";
    String inputString2 = "27 04 1997";
    ArrayList<Date> dates = new ArrayList<Date>();

    try {
        Date date1 = myFormat.parse(inputString1);
        Calendar c1 = DateToCalendar(date1);
        Date date2 = myFormat.parse(inputString2);
        Calendar c2 = DateToCalendar(date2);

        while (!areEqualDate(c1, c2)) {
            dates.add(c1.getTime());
            System.out.println (c1.getTime());
            c1.add(Calendar.DAY_OF_YEAR, 1);
        }
    } catch (ParseException e) {
        e.printStackTrace();
    }


    // ArrayList<Date> dates >> contain all dates between both given days.
}


private static boolean areEqualDate(Calendar c1, Calendar c2) {
    if (c1.get(Calendar.YEAR) != c2.get(Calendar.YEAR)) return false; 
    if (c1.get(Calendar.MONTH) != c2.get(Calendar.MONTH)) return false; 
    if (c1.get(Calendar.DAY_OF_YEAR) != c2.get(Calendar.DAY_OF_YEAR)) return false; 
    return true;
}

public static Calendar DateToCalendar(Date date) {
    Calendar cal = Calendar.getInstance();
    cal.setTime(date);
    return cal;
}

Answer 4

I like JodaTime, but this can also be done without 3rd party libraries by using java.util.Calendar. Given a Calendar object, one can use its add method to increase certain fields of the date while honoring the calendar rules (like adding 1 day to the 31st of January gets you to the 1st of February, not to the 32nd of January).

First get the dates into one Calendar object each, in the correct chronological order so adding is going in the right direction later:

    Calendar cStart = Calendar.getInstance(),
             cStop = Calendar.getInstance();

    if (date1.before(date2)) {
        cStart.setTime(date1);
        cStop.setTime(date2);
    } else {
        cStart.setTime(date2);
        cStop.setTime(date1);

date1 and date2 are the parsed Date objects from your question, for simplicity's sake.

Next, loop over an "add 1 to day-of-year" instruction until this gets you beyond the stop date:

do {
        System.out.println(pretty(cStart));
        cStart.add(Calendar.DAY_OF_YEAR, 1);
} while (cStart.before(cStop));

And lastly print the stop date

    System.out.println(pretty(cStop));

pretty() is just some mini method sending the calendar through a SDF, like the one you used for parsing the Strings in the first place.

This solution will print the date range, including the start and stop dates, and might need some tweaking around the edge cases (like date1==date2). Can be easily adapted to exclude the start and stop dates. Printing can be swapped for aggregation of course. To get a Date object from the calendar, use the getTime() method (returns a snapshot, not a live reference).

The documentation for the relevant (Gregorian)Calendar can be found here.