Issue with Gregorian Calendar [duplicate]

Question

We are using the below code snippet to get number of days for the provided month and year. For 02 and 2011, It returns the no of days as 31 ( which is not the case). for 02 and 2016, it returns the no of days as 29.

Any clues.

package Processes.BSAInvoiceInquiry.ExternalCall.PaymentStatusInquiry;
import java.util.Calendar;
import java.util.GregorianCalendar;

public class PaymentStatusInquiryJavaCode {

    protected int year = 0;
    protected int month = 0;
    protected int days = 0;

    public void invoke() throws Exception {

        PaymentStatusInquiryJavaCode a = new PaymentStatusInquiryJavaCode();

        System.out.println("Year  " + year);
        System.out.println("Month  " + month);

        Calendar calObj = new GregorianCalendar();
        calObj.set(Calendar.YEAR, year);
        calObj.set(Calendar.MONTH, month - 1);
        System.out.println("Month  " + Calendar.MONTH);
        int numDays = calObj.getActualMaximum(Calendar.DAY_OF_MONTH);
        System.out.println("No of the days in the month is   " + numDays);
        days = numDays;

    }
}

Baxley

For 02 and 2011, It returns the no of days as 31 ( which is not the case). – Baxley

You should absolutely look into Java 8's java.time package. Rock solid comfortable immutable tools. – Supercool

@DreamspacePresident our tool is still dependent on java 1.7 – Baxley

No big problem @AbdulKader. java.time has been backported to Java 6 and 7. Get ThreeTen Backport, add it to your project and start using the modern Java date and time API. And enjoy! With the trouble you’ve experienced with the old-fashioned Calendar class this will be a great relief. – Profuse

@AbdulKader I have written a new answer to the linked question. The paragraph “If you only needed a count of days in some month…” is for you. Please take a look. – Profuse

Answer 1

This is just another unexpected behavior of Calendar, see this, you can fix it by clear after the creation:

Calendar calendar = new GregorianCalendar();
calendar.clear();
calendar.set(Calendar.YEAR, 2011);
calendar.set(Calendar.MONTH, 1);
System.out.println(calendar.getActualMaximum(calendar.DAY_OF_MONTH)); //28

---

The use of outdated Calendar should be avoided. In java8, this can be done by:

YearMonth yearMonth = YearMonth.of(2011, 2);
int lengthOfMonth = yearMonth.lengthOfMonth();
System.out.println(lengthOfMonth); //28

Horny

@user66902200 didn't help , same issue – Baxley

@AbdulKader Then please post your test code. The test code in the answer works fine. – Horny

Answer 2

To complete user6690200's answer it returns 29 for 2016 because it's the 29th today and 2016 was a leap year and had a 29th of february. 2011 wasn't a leap year so it actually returns the number for the next month(March which has 31 days).

Unopened

ideally should it not be 28 – Baxley

Don't know, that's how they implemented it. – Unopened

Answer 3

try

// month 1 based    
new Calendar.Builder().setDate(year, month-1, 1).build().getActualMaximum(DAY_OF_MONTH)

the problem is none

calObj.set(DAY_OF_MONTH, 1);

Cocoon

DAY_OF_MONTH is 1 based, 0 day is a day minus – Cocoon

2011:2-1:0 is 2011:1:31 then 31, 2016:2-1:0 is 2016:1:29 then 29 – Cocoon