Java Map MCQs with answers Page - 3

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

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Q. What is the output of `map.put(1, null)` if 1 already exists with a non-null value?

  • (A) The value is not updated
  • (B) The key is removed
  • (C) The value is replaced with null
  • (D) Throws NullPointerException

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Q. Which method returns a collection view of the values contained in the map?

  • (A) values()
  • (B) getValues()
  • (C) valueSet()
  • (D) allValues()

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Q. Which Map method is used to perform a specific action for each entry?

  • (A) forEach()
  • (B) loop()
  • (C) traverse()
  • (D) mapEach()

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Q. Which of the following will throw a NullPointerException in TreeMap?

  • (A) Inserting null key
  • (B) Inserting null value
  • (C) Using containsKey() on null
  • (D) All of the above

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Q. Which method merges a new value into the Map based on the key and a remapping function?

  • (A) put()
  • (B) merge()
  • (C) join()
  • (D) combine()

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Q. What is returned by the `remove(key)` method?

  • (A) The key
  • (B) The value removed
  • (C) True if removed
  • (D) Nothing

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Q. Which of the following guarantees no duplicate keys and unsorted entries?

  • (A) TreeMap
  • (B) HashMap
  • (C) LinkedHashMap
  • (D) EnumMap

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Q. What is the time complexity of get() in HashMap in average case?

  • (A) O(log n)
  • (B) O(n)
  • (C) O(1)
  • (D) O(n log n)

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Q. Which Map implementation uses red-black tree internally?

  • (A) HashMap
  • (B) TreeMap
  • (C) Hashtable
  • (D) EnumMap

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Q. Which method replaces the value for a key only if it is already mapped?

  • (A) putIfAbsent()
  • (B) replace()
  • (C) updateIfPresent()
  • (D) setIfPresent()

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