Java Map MCQs with answers Page - 8

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. Which Map implementation uses hash table and linked list to maintain order?

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

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Q. What is returned by the `size()` method of a Map?

  • (A) Number of keys
  • (B) Number of values
  • (C) Number of key-value mappings
  • (D) Map capacity

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Q. Which of these maps throws a `NullPointerException` when `null` is used as a key?

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

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Q. Which method in the Map interface is used to copy all mappings from one map to another?

  • (A) copy()
  • (B) clone()
  • (C) putAll()
  • (D) mergeAll()

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Q. Which of the following is true about `Collections.unmodifiableMap(map)`?

  • (A) It creates a mutable map
  • (B) It creates a copy of the map
  • (C) It creates a read-only view of the map
  • (D) It removes all elements

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Q. Which type of Map allows duplicate values but unique keys?

  • (A) All Maps
  • (B) Only TreeMap
  • (C) Only HashMap
  • (D) None

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Q. What does `entrySet().iterator()` return?

  • (A) Iterator over keys
  • (B) Iterator over values
  • (C) Iterator over Map.Entry objects
  • (D) Iterator over index

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Q. What will happen if you try to modify a map created with `Map.of()`?

  • (A) Modifications are allowed
  • (B) It throws `UnsupportedOperationException`
  • (C) It silently ignores changes
  • (D) It updates only values

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Q. Which method is used to get a value or compute and store if absent?

  • (A) get()
  • (B) computeIfAbsent()
  • (C) getOrPut()
  • (D) putIfMissing()

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