Iterate between two dates including start date?

Question

Sorry for the apology for asking repeated question..

public static void main(String[] args)throws Exception {
    GregorianCalendar gcal = new GregorianCalendar();
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy.MM");
    Date start = sdf.parse("2010.01");
    Date end = sdf.parse("2010.04");
    gcal.setTime(start);
    while (gcal.getTime().before(end)) {
        gcal.add(Calendar.MONTH, 1);
        Date d = gcal.getTime();
        System.out.println(d);
    }
}

In the above code prints between dates exactly but i need to print start date also..

above code output is

Mon Feb 01 00:00:00 IST 2010
Mon Mar 01 00:00:00 IST 2010
Thu Apr 01 00:00:00 IST 2010

But i need also start date on my output..

please help me to get this Thanks in advance..

Solution 1

In my opinion this is the nicest way:

SimpleDateFormat sdf = new SimpleDateFormat("yyyy.MM");
Date start = sdf.parse("2010.01");
Date end = sdf.parse("2010.04");

GregorianCalendar gcal = new GregorianCalendar();
gcal.setTime(start);

while (!gcal.getTime().after(end)) {
    Date d = gcal.getTime();
    System.out.println(d);
    gcal.add(Calendar.MONTH, 1);
}

Output:

Fri Jan 01 00:00:00 WST 2010
Mon Feb 01 00:00:00 WST 2010
Mon Mar 01 00:00:00 WST 2010
Thu Apr 01 00:00:00 WST 2010

All we do is print the date before incrementing it, then we repeat if the date is not after the end date.

The other option is to duplicate the printing code before the while (yuck) or to use a do...while (also yuck).

Solution 2

You could use a do-while loop, but you would need to alter the end date depending on whether you want to include it or not.

The example below includes all months between 01st or 04th inclusive...

try {
    Calendar gcal = Calendar.getInstance();
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy.MM");
    Date start = sdf.parse("2010.01");
    Date end = sdf.parse("2010.05");
    gcal.setTime(start);
    do {
        Date d = gcal.getTime();
        System.out.println(d);
        gcal.add(Calendar.MONTH, 1);
    } while (gcal.getTime().before(end));
} catch (ParseException exp) {
    exp.printStackTrace();
}

Example output...

Fri Jan 01 00:00:00 EST 2010
Mon Feb 01 00:00:00 EST 2010
Mon Mar 01 00:00:00 EST 2010
Thu Apr 01 00:00:00 EST 2010

Equally, you could simply use your current code and change the start Date to one month earlier...

Date start = sdf.parse("2009.12");
//...

Updated

Another approach, based on the previous ideas...

Simply move the start date back a month before you start the loop...

Calendar gcal = Calendar.getInstance();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy.MM");
Date start = sdf.parse("2010.01");
Date end = sdf.parse("2010.04");
gcal.setTime(start);
// Move the month back by one before we start...
gcal.add(Calendar.MONTH, -1);
while (gcal.getTime().before(end)) {
    gcal.add(Calendar.MONTH, 1);
    Date d = gcal.getTime();
    System.out.println(d);
}

This is reasonably simple and allows you to supply variable dates without needing to care to remember that you need to start one month earlier....

Solution 3

You can just output it right before the start of the loop:

System.out.println(gcal.getTime());
while (gcal.getTime().before(end)) {
    gcal.add(Calendar.MONTH, 1);
    Date d = gcal.getTime();
    System.out.println(d);
}

Solution 4

then just do this:

Date lNow = gcal.getTime();
System.out.println(lNow);

while (gcal.getTime().before(end)) {
        gcal.add(Calendar.MONTH, 1);
        Date d = gcal.getTime();
        System.out.println(d);
}

Solution 5

Since Java 8, you can use the new java.time API:

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("uuuu.MM");
YearMonth date = YearMonth.parse("2010.01", formatter);
YearMonth end = YearMonth.parse("2010.05", formatter);
while (!date.isAfter(end)) {
    System.out.println(date.format(formatter));
    date = date.plusMonths(1);
}

View more solutions

Comments

[Thihara]

Why not move gcal.add(Calendar.MONTH, 1); to the end of the while body? Simpler no?

[Thihara]

I mean without moving to the do while loop.

[MadProgrammer]

@Thihara Because then it won't print the last month either. It would actually be simpler to modify either start or end date values based on which technique the OP choose to use ;)

[MadProgrammer]

I'd run with that +1 for getting both the start and end dates included

[Thihara]

Damn, outsmarted by a mad dude :-P, +1

[MadProgrammer]

@Thihara There's always more the one way to skin that cat ;) - These are just a few suggestions ;)

[George]

Wrestling with Java Calendars is one of my specialties.