reduce()

A stream operation that combines elements into one result.

What does reduce() do in Java?

reduce() — A stream operation that combines elements into one result.

import java.util.List;

class NumberTotal {
    int total(List<Integer> numbers) {
        return numbers.stream()
                .reduce(0, Integer::sum);
    }
}

Level: Freelancer · More Java terms at this level

Updated September 27, 2026