How do I calculate someone's age in Java?

Question

I want to return an age in years as an int in a Java method. What I have now is the following where getBirthDate() returns a Date object (with the birth date ;-)):

Answer 1

Here is the java code to calculate age in year, month and days.

public static AgeModel calculateAge(long birthDate) {
    int years = 0;
    int months = 0;
    int days = 0;

    if (birthDate != 0) {
        //create calendar object for birth day
        Calendar birthDay = Calendar.getInstance();
        birthDay.setTimeInMillis(birthDate);

        //create calendar object for current day
        Calendar now = Calendar.getInstance();
        Calendar current = Calendar.getInstance();
        //Get difference between years
        years = now.get(Calendar.YEAR) - birthDay.get(Calendar.YEAR);

        //get months
        int currMonth = now.get(Calendar.MONTH) + 1;
        int birthMonth = birthDay.get(Calendar.MONTH) + 1;

        //Get difference between months
        months = currMonth - birthMonth;

        //if month difference is in negative then reduce years by one and calculate the number of months.
        if (months < 0) {
            years--;
            months = 12 - birthMonth + currMonth;
        } else if (months == 0 && now.get(Calendar.DATE) < birthDay.get(Calendar.DATE)) {
            years--;
            months = 11;
        }

        //Calculate the days
        if (now.get(Calendar.DATE) > birthDay.get(Calendar.DATE))
            days = now.get(Calendar.DATE) - birthDay.get(Calendar.DATE);
        else if (now.get(Calendar.DATE) < birthDay.get(Calendar.DATE)) {
            int today = now.get(Calendar.DAY_OF_MONTH);
            now.add(Calendar.MONTH, -1);
            days = now.getActualMaximum(Calendar.DAY_OF_MONTH) - birthDay.get(Calendar.DAY_OF_MONTH) + today;
        } else {
            days = 0;
            if (months == 12) {
                years++;
                months = 0;
            }
        }
    }

    //Create new Age object
    return new AgeModel(days, months, years);
}