How to find the difference between two String ArrayList using java 8 Streams?

Question

I need to find the difference between the two string Array list using java 8 features . Current i am doing it like this

final List<String> a = new ArrayList<>();
        a.add("1");
        a.add("2");
        a.add("3");

        final List<String> b = new ArrayList<>();
        b.add("1");
        b.add("2");
        b.add("4");

        final List<String> result = a.stream().filter((s) -> b.stream().noneMatch(s::equals))
                .collect(Collectors.toList());
        final List<String> result2 = b.stream().filter((s) -> a.stream().noneMatch(s::equals))
                .collect(Collectors.toList());

        System.out.println(result);
        System.out.println(result2);

        final List<String> FinalResult = java.util.stream.Stream.concat(result.stream(), result2.stream())
                .distinct()
                .collect(Collectors.toList());   

        System.out.println(FinalResult);

Can any one suggest a cleaner and shorter code for the same thing ? I am feeling it can be done in some other simpler way .

You can do something like `Stream.concat(a.stream(), b.stream()).filter(s -> a.contains(s) != b.contains(s)).collect(Collectors.toList());` — , Jun 09 '18 at 08:00
@TalOhana is it asking m to make a and b inside filter as final . why is it required ? i am not willing to make it final — user_531, Jun 09 '18 at 08:48

score 3 · Answer 1 · edited Jun 09 '18 at 07:59

3

You can do the same thing using below code:

List<String> result = b.stream()
                       .filter(not(new HashSet<>(a)::contains))
                       .collect(Collectors.toList());

private static <T> Predicate<T> not(Predicate<T> predicate) {
    return predicate.negate();
}

Hope it helps.

edited Jun 09 '18 at 07:59

Oleksandr Pyrohov

14,685
6
61
90

answered Jun 09 '18 at 07:52

Antariksh

508
8
17

this is awesome ! thank you – user_531 Jun 09 '18 at 08:02
your above code only gives elements of list b and that are not in A i.e B-A . but i need A-B + B-A elements – user_531 Jun 09 '18 at 08:54

How to find the difference between two String ArrayList using java 8 Streams?

1 Answers1