Java 12: Collectors.teeing merges two collectors

teeing feeds each element to two collectors and combines their results.

Code

record Stats(long count, int sum) {}
List<Integer> nums = List.of(2, 4, 6, 8);
Stats s = nums.stream().collect(Collectors.teeing(
        Collectors.counting(),
        Collectors.summingInt(Integer::intValue),
        (count, sum) -> new Stats(count, sum)));
System.out.println(s);

Output

Stats[count=4, sum=20]

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Published 2026-07-26