Java stream reduce to map

Question

I got array list of strings, how could I reduce them to hash map

Input: [a, b, a, a, c, x]

Output: {(a: 3), (b: 1), (c: 1), (x: 1)}

PS. I searched for this. I need to do that with reduce not with frequency counting as in other questions, because my question is a simplified real task.

You can do like: `Map result = Arrays.stream(str) .reduce(new HashMap<>(), (hashMap, e) -> {hashMap.merge(e,1,Integer::sum);return hashMap;}, (m, m2) -> {m.putAll(m2);return m;});` however other solutions are more readable and concise. — Hadi J, May 31 '20 at 13:32
@HadiJ Thanks, It is not about readability, I simplified my real task for the question, that is why I asked exactly about reduce. Thank you once again. — Егор Лебедев, May 31 '20 at 13:35

score 9 · Accepted Answer · answered Jun 01 '20 at 07:51

Thanks @HadiJ for answer

Map<String,Integer> result = Arrays.stream(str)
    .reduce(new HashMap<>(), (hashMap, e) -> {
        hashMap.merge(e, 1, Integer::sum);
        return hashMap;
    },
    (m, m2) -> {
        m.putAll(m2);
        return m;
    }
);

Java stream reduce to map

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