How to get list of months & years between two dates

Question

I need your help in getting the list of months and the years in String between two dates. The user will enter two dates in the String format of:

String date1 ="JAN-2015";
String date2 ="APR-2015";

So the result should be:

• Jan-2015
• FEB-2015
• MAR-2015

I tried using the following code but it gave me wrong results:

List<Date> dates = new ArrayList<Date>();

String str_date ="JAN-2015";
String end_date ="APR-2015";

DateFormat formatter ; 

formatter = new SimpleDateFormat("MMM-yyyy");
Date  startDate = formatter.parse(str_date); 
Date  endDate = formatter.parse(end_date);
long endTime =endDate.getTime() ; 
long curTime = startDate.getTime();
while (curTime <= endTime) {
    dates.add(new Date(curTime));
    curTime ++;
}
for(int i=0;i<dates.size();i++){
    Date lDate =(Date)dates.get(i);
    String ds = formatter.format(lDate);    
    System.out.println(ds);
}

Answer 1

Using the less code possible and basic java libraries and getting the result you asked for. So you can modify the date1 and date2 variables.

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;

public class Main {
    public static void main(String[] args) {
        String date1 = "JAN-2015";
        String date2 = "APR-2015";

        DateFormat formater = new SimpleDateFormat("MMM-yyyy");

        Calendar beginCalendar = Calendar.getInstance();
        Calendar finishCalendar = Calendar.getInstance();

        try {
            beginCalendar.setTime(formater.parse(date1));
            finishCalendar.setTime(formater.parse(date2));
        } catch (ParseException e) {
            e.printStackTrace();
        }

        while (beginCalendar.before(finishCalendar)) {
            // add one month to date per loop
            String date =     formater.format(beginCalendar.getTime()).toUpperCase();
            System.out.println(date);
            beginCalendar.add(Calendar.MONTH, 1);
        }
    }
}

Answer 2

In case your Java version is < 8 you could use Calendar as follows:

private final static DateFormat formatter = new SimpleDateFormat("MMM-yyyy", Locale.ENGLISH);

public static void main(String[] args) throws ParseException {
    Calendar startDate = stringToCalendar("Jan-2015");
    Calendar endDate = stringToCalendar("Apr-2015");

    while (startDate.before(endDate)) {
        System.out.println(formatter.format(startDate.getTime()));
        startDate.add(Calendar.MONTH, 1);
    }
}

private static Calendar stringToCalendar(String string) throws ParseException {     
    Date date = formatter.parse(string);
    Calendar calendar = Calendar.getInstance();
    calendar.setTime(date);
    return calendar;
}

If you have a luxury of Java 8 then the code becomes more simple:

public static void main(String[] args) {        
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MMM-yyyy", Locale.ENGLISH);
    YearMonth startDate = YearMonth.parse("Jan-2015", formatter);
    YearMonth endDate = YearMonth.parse("Apr-2015", formatter);

    while(startDate.isBefore(endDate)) {
        System.out.println(startDate.format(formatter));
        startDate = startDate.plusMonths(1);
    }
}