AgeCalculator

AgeCalculator.java

public class AgeCalculator {

    private int days;
    private int months;
    private int years;

    AgeCalculator(int days, int months, int years) {
        this.days = days;
        this.months = months;
        this.years = years;
    }

    public int getDays() {
        return days;
    }

    public int getMonths() {
        return months;
    }

    public int getYears() {
        return years;
    }

    public boolean isAboveMinimumAgeRequirement() {
        return getYears() >= 18;
    }

    @Override
    public String toString() {
        return years + " Years, " + months + " Months, " + days + " Days";
    }

    public static AgeCalculator calculateAge(Calendar birthDay) {
        int years;
        int months;
        int days;

        long currentTime = System.currentTimeMillis();
        Calendar now = Calendar.getInstance();
        now.setTimeInMillis(currentTime);

        years = now.get(Calendar.YEAR) - birthDay.get(Calendar.YEAR);
        int currMonth = now.get(Calendar.MONTH) + 1;
        int birthMonth = birthDay.get(Calendar.MONTH) + 1;

        months = currMonth - birthMonth;

        //and calculate the number of months.
        if (months < 0) {
            years--;
            months = 12 - birthMonth + currMonth;
            if (now.get(Calendar.DATE) < birthDay.get(Calendar.DATE))
                months--;
        } else if (months == 0 && now.get(Calendar.DATE) < birthDay.get(Calendar.DATE)) {
            years--;
            months = 11;
        }

        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;
            }
        }

        return new AgeCalculator(days, months, years);
    }
}