Java Interview Questions · interview question

Which practice avoids a common mistake with map, flatMap, and reduce?

Multiple choiceMediumjava-interview-2026interviewjavapitfall

Ignore the map, flatMap, and reduce issue and rely on team discipline instead of APIs or contracts.Prefer the version of map, flatMap, and reduce that makes behavior less predictable as long as the code compiles.Do not introduce hidden side effects inside stream transformations just because the syntax is compact.Silence the map, flatMap, and reduce problem by using raw types, broad catches, or shared mutable state.

Answer and explanation

Correct answer

C. Do not introduce hidden side effects inside stream transformations just because the syntax is compact.

Why

Do not introduce hidden side effects inside stream transformations just because the syntax is compact. This is a common failure mode in real Java code and a frequent interview follow-up.

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Which practice avoids a common mistake with map, flatMap, and reduce?

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