Analog of ORACLE function MONTHS_BETWEEN in Java

Question

Does Java have some analog of Oracle\'s function MONTHS_BETWEEN?

Answer 1

I've the same problem and following the Oracle MONTHS_BETWEEN I have made some changes to @alain.janinm and @Guerneen4 answers in order to correct some cases:

Consider months between 31/07/1998 and 30/09/2013 ("dd/MM/yyyy") Oracle result : 182 Java method from @Guerneen4 answer : 181.96774193548387

The problem is that according to specification if date1 and date2 are both last days of months, then the result is always an integer.

For easy understanding here you can find Oracle MONTHS_BETWEEN specifications: https://docs.oracle.com/cd/B19306_01/server.102/b14200/functions089.htm. I copy here to summarize:

"returns number of months between dates date1 and date2. If date1 is later than date2, then the result is positive. If date1 is earlier than date2, then the result is negative. If date1 and date2 are either the same days of the month or both last days of months, then the result is always an integer. Otherwise Oracle Database calculates the fractional portion of the result based on a 31-day month and considers the difference in time components date1 and date2."

Here's the changes that I've done get the closest result to the Oracle's months_between() function :

public static double monthsBetween(Date startDate, Date endDate) {
    Calendar calSD = Calendar.getInstance();
    Calendar calED = Calendar.getInstance();

    calSD.setTime(startDate);
    int startDayOfMonth = calSD.get(Calendar.DAY_OF_MONTH);
    int startMonth = calSD.get(Calendar.MONTH);
    int startYear = calSD.get(Calendar.YEAR);

    calED.setTime(endDate);
    int endDayOfMonth = calED.get(Calendar.DAY_OF_MONTH);
    int endMonth = calED.get(Calendar.MONTH);
    int endYear = calED.get(Calendar.YEAR);

    int diffMonths = endMonth - startMonth;
    int diffYears = endYear - startYear;
    int diffDays = calSD.getActualMaximum(Calendar.DAY_OF_MONTH) == startDayOfMonth
            && calED.getActualMaximum(Calendar.DAY_OF_MONTH) == endDayOfMonth ? 0 : endDayOfMonth - startDayOfMonth;

    return (diffYears * 12) + diffMonths + diffDays / 31.0;
}