Question

I’m writing a program that asks the user for their birthdate and then calculates their age in years of different planets. I am not suppose to assume how the birthdate is to be entered except that there is one white space between each number.

The code I have right now does not meet these specifications right now and I’m not sure how to write it otherwise. I am also having problem calculating what my age would be today. When I enter my birthdate and print out age, it currently tells me that I’m 407 yet when I print out dateBirth and today, both of those dates are correct.

System.out.print("Please enter your birthdate (mm dd yyyy): ");
birthdate = scan.nextLine();

DateFormat df = new SimpleDateFormat("MM dd yyyy");
Date dateBirth = df.parse(birthdate);
Calendar calBirth = new GregorianCalendar();
calBirth.setTime(dateBirth);

Calendar calDay = new GregorianCalendar();
today = calDay.getTime();
age = (today.getTime() - dateBirth.getTime()) / (1000 * 60 * 60 * 24 * 365);

Answer 1

1000 * 60 * 60 * 24 * 365 is actually 31536000000 which is bigger than Integer.MAX_VALUE this causes an overflow. As an integer it would be evaluated to 1471228928 which leads to the wrong result.

The solution is append the letter L to one of your constants

long div = ( 1000 * 60 * 60 * 24 * 365L );
long age = ( today.getTime() - dateBirth.getTime() ) / div;