Question

For example, I have two objects:

Icecream ice1 = new Icecream(vanilla, newDate(11, 09, 09));
Icecream ice2 = new Icecream(choko, newDate(10, 08, 08));
// where first argument is a String and second argument is a Date 

how can I print the out so that they will be ordered by the date starting from earliest? (toStrign method is already configured)

Output sholud be:

Vanilla, 10-08-08
Vanilla, 11-09-09

Thank you!

Answer 1

You can define a natural ordering for your class IceCream by implementing the Comparator interface.

public class IceCream implements Comparator{
    // ...
    final String name; 
    final Date date;
    public Icecream(String name, Date date){
       this.name = name;
       this.date = date;
    }
    public int compare(Object o1, Object o2) {
        return ((IceCream)o1).date.compareTo(((IceCream)o2).date);
    }
}