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

Difficulty:

Easy

Questions:

1

Time Limit:

2 minutes

Passing Score:

100%

Question

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

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

Hint

Focus on the behavior or tradeoff, not just the keyword.

Answer and rationale

Correct answer: C. map keeps one output element per input element, while flatMap can expand or collapse nested structures.

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.

Track: Java