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!
Implement your own comparator and call sort on the collection. Good tutorial is here for example:
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);
}
}
Comparable interface, not Comparator. And in either case, you should be using the parameterized type, not the raw type, so it should be public class IceCream implements Comparable<IceCream>.
Commented
Dec 12, 2011 at 19:10
Make a custom comparator for your Icecream class.
class DateComparator implements Comparator {
public int compare(Object ic1, Object ic22){
/*
* parameter are of type Object, so we have to downcast it
* to Icecream objects
*/
Date ic1Date = ((Icecream)ic1).getDate();
Date ic2Date = ((Icecream)ic2).getDate();
return ic1Date.compareTo(ic2Date);
}
}
I would make two classes, one that implements Comparator and one Sorter that handles the sorting of an array, with a comparator as parameter. Then put the ice creams in a array and call your sort method in Sorter.
