How can I sort Arrays in a Collection?

Question

I have a a List of Objects. Those Objects have (amongst others) a private int Array (if it helps, I can transfer it into a List). There is a public Getter for this Array. All Arrays are the same size.

I want to sort the Object based on their Arrays like this:

Unsorted:
{[0, 1, 4, 5], 
 [0, 0, 2, 3],
 [0, 1, 1, 2]}

Sorted:
{[0, 0, 2, 3],
 [0, 1, 1, 2],
 [0, 1, 4, 5]}

In Words (it's called lexicographical):

• compare the first int of each array
• if they are equal, compare the next int of each array (and so on)
• if they aren't equal the result of the comparison is the end result.

I manage to search them for e.g. only the first element of the array with a normal Comparator but I don't know how to search them for all.

Answer 1

A nice Java 8 solution is

static final Comparator<CustomObject> COMPARATOR = (o1, o2) -> {
    int[] arr1 = o1.getArray();
    int[] arr2 = o2.getArray();
    return IntStream.range(0, arr1.length)
                    .map(i -> Integer.compare(arr1[i], arr2[i]))
                    .filter(i -> i != 0)
                    .findFirst()
                    .orElse(0);
};

Then, given a List<CustomObject>, you can do

list.sort(COMPARATOR);

(The Comparator only works for arrays of the same length. You may want to modify it).