import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Collections;
import java.util.Comparator;
import java.util.GregorianCalendar;
import java.util.Iterator;
import java.util.List;

public class DataStructures {

    public static void main(String[] args) {
        List<Person> people = new ArrayList<Person>();
        people.add(new Person("barney", new GregorianCalendar(1980, Calendar.JUNE, 10)));
        people.add(new Person("heather", new GregorianCalendar(1980, Calendar.FEBRUARY, 12)));
        people.add(new Person("emery", new GregorianCalendar(2005, Calendar.AUGUST, 12)));

        Iterator<Person> itr = people.iterator();
        int sum = 0;
        while (itr.hasNext()) {
            sum += itr.next().getAge();
        }
        System.out.println("Average Age: " + sum / people.size());
        
        Collections.sort(people, new Comparator<Person>() {
            public int compare(Person p1, Person p2) {
                return p1.name.compareTo(p2.name);
            }
        });
        
        System.out.println(people);
    }

    
    static class Person {
        public String name;
        public Calendar dob;

        public Person(String name, Calendar dob) {
            this.name = name;
            this.dob = dob;
        }
        
        public int getAge() {
            // cheater!
            return (int) ((new GregorianCalendar().getTimeInMillis() - dob.getTimeInMillis()) / 1000 / 86400);
        }
        
        public String toString() {
            return name + " (" + new SimpleDateFormat("MMM d, yyy").format(dob.getTime()) + ")";
        }
    }
}