Java: Partition a stream with Collectors.partitioningBy

partitioningBy splits elements into a Map<Boolean, List> of matches and non-matches.

Code

Map<Boolean, List<Integer>> parts = IntStream.rangeClosed(1, 8).boxed()
        .collect(Collectors.partitioningBy(n -> n % 2 == 0));
System.out.println("even: " + parts.get(true));
System.out.println("odd:  " + parts.get(false));

Output

even: [2, 4, 6, 8]
odd:  [1, 3, 5, 7]

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Published 2026-07-26