How to sort int[] with multi-line lambda expression in Java

Question

This question has an answer for how to sort a List with a multi-line lambda expression:

list.sort((o1, o2) -> {
    int cmp = o1.getGroup().compareTo(o2.getGroup());
    if (cmp == 0)
        cmp = Integer.compare(o1.getAge(), o2.getAge());
    if (cmp == 0)
        cmp = o1.getName().compareTo(o2.getName());
    return cmp;

});

Unfortunately, this does not seem to work for a raw array int[] arr:

Arrays.sort(arr, (int1, int2) -> {
    // some lambda, various if-else statements for example
});

How to use a multi-line lambda expression in Arrays.sort() to sort a raw array?

I'm fine with any other approach (does not have to use Arrays.) as long as it uses lambda expressions (no comparators).

Does this answer your question? java comparator for arrays sort — Savior
– Savior, Commented Apr 7, 2020 at 16:05
Not very efficient, but arr = Arrays.stream(arr).boxed().sorted((int1, int2) -> { /* your logic */ }).mapToInt(Integer::intValue).toArray(); would work. — Holger
– Holger, Commented Apr 7, 2020 at 16:10

WJS · Accepted Answer · 2020-04-07 17:50:22Z

1

If you're intent on doing it using only lambdas then this will work with both lists and arrays. This presume your group and age fields are ints.

        Comparator<Item> comp = (o1, o2) -> {
            int cmp = Integer.compare(o1.getGroup(), o2.getGroup());
            cmp = cmp == 0 ? Integer.compare(o1.getAge(), o2.getAge()) : cmp;
            cmp = cmp == 0 ? o1.getName().compareTo(o2.getName()) : cmp;
            return cmp;
        };

        list.sort(comp);

        Arrays.sort(items, comp);

But I would use a List and do it as follows:

    list.sort(Comparator.comparing(Item::getGroup)
                .thenComparing(Item::getAge)
                .thenComparing(Item::getName));

And even your lambda expression is a comparator. You can't compare without some sort of Comparator no matter how you construct it.

edited Apr 7, 2020 at 17:50

answered Apr 7, 2020 at 17:43

WJS

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