sort an arraylist of arraylist of integers

Question

I am looking to sort an arraylist of arraylist of integers and I require help?

I was informed that I need to implement comparator or comparable and then use the coll

Answer 1

No error check for null lists, but here it is.

List> list = Arrays.asList(Arrays.asList(10, 5, 4), 
        Arrays.asList(3, 2, 1), Arrays.asList(7, 8, 6));
for (List l : list) {
    Collections.sort(l);
}
Collections.sort(list, new Comparator>() {
    public int compare(List o1, List o2) {
        return o1.get(0).compareTo(o2.get(0));
    }
});
System.out.println(list);

With Java 8 it gets even more concise:

List> list = Arrays.asList(Arrays.asList(10, 5, 4),
                Arrays.asList(3, 2, 1), Arrays.asList(7, 8, 6));
list.forEach(Collections::sort);
Collections.sort(list, (l1, l2) -> l1.get(0).compareTo(l2.get(0)));
System.out.println(list);