Java Streams MCQs with answers Page - 5

You will find multiple-choice questions (MCQs) related to #Java Streams here. Go through these questions to prepare effectively for your upcoming exams and interviews.

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Q. What happens if `stream()` is called on a null List?

  • (A) Empty stream is returned
  • (B) NullPointerException is thrown
  • (C) Compilation error
  • (D) All elements are removed

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Q. Which method would you use to get the maximum value from a Stream?

  • (A) max()
  • (B) maximum()
  • (C) findMax()
  • (D) collectMax()

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Q. What is returned by `reduce()` when no identity is provided and the stream is empty?

  • (A) 0
  • (B) null
  • (C) Optional.empty()
  • (D) IllegalStateException

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Q. Which of the following is not a valid intermediate operation?

  • (A) map()
  • (B) filter()
  • (C) collect()
  • (D) limit()

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Q. Which method returns true if the stream contains no elements?

  • (A) isEmpty()
  • (B) noneMatch(x -> true)
  • (C) count() == 0
  • (D) Both b and c

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Q. Which method is used to create a Stream of primitive ints?

  • (A) IntStream.of()
  • (B) Stream.ofInt()
  • (C) IntStream.stream()
  • (D) Stream.of(int[])

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Q. Which of the following types is a primitive specialization of Stream?

  • (A) DoubleList
  • (B) LongList
  • (C) IntStream
  • (D) StringStream

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Q. What does `flatMapToInt()` return?

  • (A) Stream<Integer>
  • (B) IntStream
  • (C) DoubleStream
  • (D) LongStream

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Q. What is the difference between `map()` and `flatMap()`?

  • (A) map flattens, flatMap transforms
  • (B) map transforms, flatMap flattens nested streams
  • (C) Both do the same
  • (D) flatMap does not exist

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Q. Which collector is used to partition a stream into two groups?

  • (A) Collectors.toMap()
  • (B) Collectors.groupingBy()
  • (C) Collectors.partitioningBy()
  • (D) Collectors.dividingBy()

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