Check the difference of the date's month

[Hin Wong]

I have a start date and an end date, I want to check if the start date is 6 month earlier than the end date. How should I do that? I have the if else statement at the end, but I am not sure how to fix this if else statement. Help will be appreciated

startdate = 1/1/2015
enddate = 12/1/2015
 
public void String getMonthsDifference(Date startdate, Date enddate) {
 
    if (startdate.get(Calendar.MONTH) < enddate.get(Calendar.MONTH) {
        //do something
       //Here is my pesudocode
 
         //Check to see if startdate is 6 month's eariler than enddate
         //If startdate is 6 month eariler than enddate
         //startdate month increase by one
         //startdate change to (enddate - 6)
         //
          
         //else
         //startdate change to (enddate-6)
         //
         
 
    }  else{
        // do this
    }
}

[Campbell Ritchie]

Welcome to the Ranch

If at all possible stop using Calendar and Date. Use the new date‑time classes. Otherwise you will have to do things like

Calendar c1 = new GregorianCalendar(...);
c1.set(2015, Calendar.AUGUST, 4);
Calendar c2 = new GregorianCalendar(...);
c2.set(...);
Calendar c3 = c2.clone();
c3.add(Calendar.MONTH, SIX);
if (c3.compareTo(c1) > 0)
{
   ...
}

That is horrible code. I am sure somebody else will find a better way to add six months.

[Hin Wong]

Hello, thank you for your reply. I am not sure if I did it the right way, but what I did is I calculate the difference between two date and than use that value to compare it. Something like this, but it seems it doesn't work

Here is my code

 private static String[] getDateUpdate(Calendar cal2, Calendar run_to_date_cal, Date date_int, Date date_to_end){
    	 
         
    	 SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy");
    	 
    	 String startDateValue = sdf.format(cal2.getTime());
    	 String endDateValue = sdf.format(run_to_date_cal.getTime());
    	 
    	 int monthDifference = run_to_date_cal.get(Calendar.MONTH) - cal2.get(Calendar.MONTH);
    	 
    	 //if startdate's month 6 months earlier than enddate's month
    	 
    	 System.out.println(monthDifference);
   	 if(monthDifference > 6){

    		  System.out.println("True");

    		// add one month to startdate
    		 cal2.add(Calendar.MONTH, 1);
    		 
    		 run_to_date_cal.get(Calendar.MONTH);
    		 
    		
    		 
    		 run_to_date_cal.add(Calendar.MONTH, -6);
    		 
    		 cal2 = (Calendar) run_to_date_cal.clone();
    		 	 
    		 
    		 //set enddate = today's execution date
    		 Calendar updateCurrentTime = Calendar.getInstance();
    		 
    		 
    		// run_to_date_cal = (Calendar) updateCurrentTime;
    		 
    		 System.out.println(run_to_date_cal.getTime());
    		 
    	 } else{
    		 
    		 System.out.println("NO");
    		 
    		 run_to_date_cal.add(Calendar.MONTH, -6);
    		 
    		 
    		 //set enddate = today's execution date
    		Calendar updateCurrentTime = Calendar.getInstance();
    		 run_to_date_cal = (Calendar) updateCurrentTime;
    	 }

    	
    	 return new String[] {startDateValue, endDateValue};
    }

[Campbell Ritchie]

Converting things to Strings and back looks like the wrong way to do it. You cannot simply take month numbers and see whether they differ by 6; if you go from now to next March the month numbers will be 7 and 2 which differ by 5. And the wrong way, even though the difference is 7 months. That is why you should get rid of the old time and date classes. You can use local dates to create a Duration object, and I am sure you can work out whether that Duration is six months or more. You can create a Period object equivalent to six months and then compare that to the duration object you have from earlier.

But these classes are only available in Java8.

Don't use underscores_in_variable_names, only in CONSTANT_NAMES. Use camelCase for variableNames.