Java Collections Framework MCQs

The Java Collections Framework is the backbone of Java’s data storage and manipulation capabilities, offering developers a rich set of tools for managing collections of objects. This article, “Java Collections Framework MCQs,” delves into this essential Java topic, covering various collection classes like ArrayList, LinkedList, HashSet, and HashMap. It also explores the usage of iterators and the versatile foreach loop for efficient collection traversal.

Furthermore, this resource navigates through the core interfaces of the Java Collections Framework, such as List, Set, and Map, providing multiple-choice questions (MCQs) to bolster your understanding of this critical area of Java programming. Whether you’re preparing for interviews or seeking to enhance your proficiency in handling data structures, these MCQs offer a practical way to reinforce your knowledge of Java’s Collections Framework.

1.) Which data structure allows elements to be stored in a contiguous memory location?

A) ArrayList
B) LinkedList
C) HashSet
D) HashMap

Answer: Option A

Explanation: An ArrayList stores elements in a contiguous memory location, providing fast random access.

2.) In terms of performance, which collection is generally faster for adding and removing elements at the beginning?

A) ArrayList
B) LinkedList
C) HashSet
D) HashMap

Answer: Option B

Explanation: LinkedList is generally faster for adding and removing elements at the beginning because it involves changing references.

3.) Which data structure is more suitable for frequent insertions and deletions at both ends (beginning and end) of the collection?

A) ArrayList
B) LinkedList
C) HashSet
D) HashMap

Answer: Option B

Explanation: LinkedList is more suitable for frequent insertions and deletions at both ends due to its structure.

4.) Which collection maintains the insertion order of elements?

A) ArrayList
B) LinkedList
C) HashSet
D) HashMap

Answer: Option A

Explanation: ArrayList maintains the order of elements based on their insertion.

5.) Which collection interface allows elements to be stored in an ordered sequence and provides positional access?

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

Answer: Option C

Explanation: The List interface allows elements to be stored in an ordered sequence and provides positional access based on indexes.

6.) What is the time complexity for accessing an element by index in an ArrayList?

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

Answer: Option A

Explanation: Accessing an element by index in an ArrayList is a constant-time operation.

7.) Which collection does not allow duplicate elements and does not maintain insertion order?

A) ArrayList
B) LinkedList
C) HashSet
D) HashMap

Answer: Option C

Explanation: HashSet does not allow duplicate elements and does not maintain any specific order.

8.) Which interface in Java provides support for iterating over the elements of a collection in both forward and backward directions?

A) Iterable
B) Collection
C) List
D) BidirectionalIterable

Answer: Option C

Explanation: The List interface provides support for bidirectional (forward and backward) iteration.

9.) What is the primary difference between a HashSet and a HashMap?

A) HashSet stores key-value pairs, while HashMap stores elements.
B) HashSet allows duplicate elements, while HashMap does not.
C) HashSet does not maintain any order, while HashMap maintains key-value associations.
D) HashSet provides faster access to elements than HashMap.

Answer: Option C

Explanation: HashSet is a set, while HashMap is a key-value mapping collection.

10.) In a HashMap, what is the purpose of the key?

A) It is used as an index for accessing values.
B) It uniquely identifies the value.
C) It determines the order of elements.
D) It is not used in HashMap.

Answer: Option A

Explanation: In a HashMap, the key is used as an index to access the associated value.

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