86. Is hashmap an ordered collection.

1. 1. False

   
   
   

   2. True

   
   
   

   3. Only A

   
   
   

   4. Only B

   
   
   

   5. A and B both

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   Hashmap outputs in the order of hashcode of the keys. So it is unordered but will always have same result for same set of keys.

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87. While finding the correct location for saving key value pair, how many times the key is hashed?

1. 1. 0

   
   
   

   2. 1

   
   
   

   3. 2

   
   
   

   4. 3

   
   
   

   5. unlimited till bucket is found

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   The key is hashed twice; first by hashCode() of Object class and then by internal hashing method of HashMap class.

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88. What happens if we put a key object in a HashMap which exists?

1. 1. The old object is removed from the map

   
   
   

   2. It throws an exception as the key already exists in the map

   
   
   

   3. The new object replaces the older object

   
   
   

   4. The new object is discarded

   
   
   

   5. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   HashMap always contains unique keys. If same key is inserted again, the new object replaces the previous object.

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89. What is the premise of equality for IdentityHashMap?

1. 1. Hashcode equality

   
   
   

   2. Length equality

   
   
   

   3. Name equality

   
   
   

   4. Reference equality

   
   
   

   5. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   IdentityHashMap is rarely used as it violates the basic contract of implementing equals() and hashcode() method.

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90. Which of the below does not implement Map interface?

1. 1. Hashtable

   
   
   

   2. HashMap

   
   
   

   3. Vector

   
   
   

   4. EnumMap

   
   
   

   5. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   Vector implements AbstractList which internally implements Collection. Others come from implementing the Map interface.

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