Java order a collection

Question

I have this map:

Map<Integer,List<EventiPerGiorno>> mapEventi=new HashMap<Integer,List<EventiPerGiorno>>();

where EventiPerGiorno is a Comparable object. How can I get a sorted list from the map?

I tried with

Collection<List<EventiPerGiorno>> collection=mapEventi.values()
Comparable.sort(collection);

But Comparable.sort() doesn't like the list as comparable. Is there a ComparableList?

EDIT

this is the comparable method...

public class EventiPerGiorno implements Comparable<EventiPerGiorno>{


    @Override
    public int compareTo(EventiPerGiorno o) {
        return this.getPrimoSpettacolo().compareTo(o.getPrimoSpettacolo());
    }

}

Answer 1

Java Collections don't have any order associated with them. You could turn the Collection into a List first and then sort it.

Collection<List<EventiPerGiorno>> collection = mapEventi.values()
YourComparableList<List<EventiPerGiorno>> list = new YourComparableList(collection);
Collections.sort(list);

For this, you will need to create some sort of List that implements Comparable. See How do I correctly implement Comparable for List in this instance? for an example.

Note that this is sorting the objects of type List<EventiPerGiorno>, not the objects of type EventiPerGiorno. If you are interested in sorting the latter, you might want this instead:

ArrayList<EventiPerGiorno> bigList = new ArrayList<EventiPerGiorno>();
for (List<EventiPerGiorno> list : mapEventi.values()) {
    bigList.addAll(list);
}
Collections.sort(bigList);