Java Streams MCQs with answers Page - 6

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Q. What is the default behavior of `sorted()`?

  • (A) Sorts by hash code
  • (B) Sorts using natural order
  • (C) Sorts by toString()
  • (D) Sorts by insertion order

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Q. How can you avoid a `NullPointerException` while using streams?

  • (A) Use empty lists only
  • (B) Use null-safe streams like `Optional.ofNullable()`
  • (C) Avoid using `stream()`
  • (D) Convert everything to primitive types

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Q. What is the result of `Stream.of(1, 2, 3).reduce(1, (a, b) -> a * b)`?

  • (A) 6
  • (B) 12
  • (C) 0
  • (D) 7

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Q. Which method will throw if there is no element in the stream?

  • (A) findFirst().orElse(null)
  • (B) findFirst().get()
  • (C) findAny().isPresent()
  • (D) findFirst().orElseThrow()

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Q. What is the output type of `Collectors.toMap()`?

  • (A) List
  • (B) Set
  • (C) Map
  • (D) Queue

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Q. Which stream operation is best suited to calculate the average of a list of numbers?

  • (A) reduce()
  • (B) collect(Collectors.summingInt())
  • (C) mapToInt().average()
  • (D) count()

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Q. What does `Collectors.toCollection(TreeSet::new)` do?

  • (A) Returns a HashSet
  • (B) Returns a TreeSet containing sorted elements
  • (C) Returns a List
  • (D) Returns a Map

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Q. What happens if duplicate keys are provided to `Collectors.toMap()`?

  • (A) Last one wins
  • (B) Exception is thrown
  • (C) Ignored
  • (D) Merged automatically

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