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In Java, which comparison about map, flatMap, and reduce is accurate?

Multiple choiceEasyjava-interview-2026interviewjavacomparison

The oldest option related to map, flatMap, and reduce is always the right production choice regardless of context.Differences around map, flatMap, and reduce are mostly cosmetic, so correctness and maintainability do not change.Map keeps one output element per input element, while flatMap can expand or collapse nested structures.There is no practical difference in behavior, performance, or API design when map, flatMap, and reduce is involved.

Answer and explanation

Correct answer

C. Map keeps one output element per input element, while flatMap can expand or collapse nested structures.

Why

map keeps one output element per input element, while flatMap can expand or collapse nested structures. This is the comparison that usually separates memorization from understanding.

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In Java, which comparison about map, flatMap, and reduce is accurate?

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