MCQs on Collections and Basics of Immutability | Scala
Dive deep into Scala collections such as Lists, Sets, Maps, and Tuples. Understand the essence of immutability and learn essential operations on collections with this comprehensive MCQ set.
Collections and Basics of Immutability in Scala
1. Lists, Sets, Maps, and Tuples
- What is the key characteristic of a
Listin Scala?- A) It is mutable
- B) It maintains insertion order
- C) It does not allow duplicate elements
- D) It is unordered
- How is an empty
Listdefined in Scala?- A)
List() - B)
new List - C)
List.empty - D) Both A and C
- A)
- What distinguishes a
Setin Scala?- A) It allows duplicate elements
- B) It automatically sorts elements
- C) It contains unique elements
- D) It has a fixed size
- How do you create a
Mapin Scala?- A)
Map(key -> value) - B)
new Map(key = value) - C)
Map{key, value} - D)
Map(key = value)
- A)
- What is a Tuple in Scala?
- A) A mutable collection
- B) A sequence of immutable elements
- C) A special kind of List
- D) A key-value pair
- How do you access elements in a Tuple?
- A) Using square brackets
- B) Using
tupleName(index) - C) Using
.indexnotation (e.g.,.1,.2) - D) Using the
get()method
- What is the maximum number of elements allowed in a Tuple in Scala?
- A) 10
- B) 15
- C) 22
- D) 25
- Which Scala collection is ordered and immutable by default?
- A) List
- B) Set
- C) Map
- D) Tuple
- What happens when you try to access a non-existent key in a
Map?- A) Throws a
NullPointerException - B) Returns
None - C) Returns
null - D) Throws a
NoSuchElementException
- A) Throws a
- Which method checks if a key exists in a
Map?- A)
containsKey - B)
exists - C)
keyExists - D)
contains
- A)
2. Immutability and Immutables
- What does immutability mean in Scala collections?
- A) Collections cannot grow or shrink
- B) Elements cannot be added, modified, or removed
- C) Collections cannot be sorted
- D) Collections cannot hold duplicate elements
- Which of these is an immutable collection in Scala?
- A) Array
- B) MutableList
- C) List
- D) Buffer
- How do you create an immutable
Set?- A)
Set(1, 2, 3) - B)
new immutable.Set(1, 2, 3) - C)
ImmutableSet(1, 2, 3) - D)
Set.immutable(1, 2, 3)
- A)
- Can immutable collections in Scala be updated?
- A) Yes, by modifying them directly
- B) No, they are permanently fixed
- C) Yes, but it creates a new instance
- D) No, unless they are converted to mutable
- What is the advantage of immutability in collections?
- A) Easier debugging
- B) Thread safety
- C) Predictable behavior
- D) All of the above
- Which of the following operations is not allowed on an immutable
List?- A) Adding elements
- B) Accessing elements
- C) Traversing elements
- D) Mapping elements
- How do you convert a mutable collection to immutable in Scala?
- A)
collection.toImmutable - B)
collection.toSeq - C)
collection.toList - D)
collection.to[immutable]
- A)
- Why are immutable collections preferred in functional programming?
- A) They ensure side effects are minimized
- B) They are faster than mutable collections
- C) They consume less memory
- D) They allow in-place modifications
- What is the return type when updating an immutable collection?
- A) The same collection instance
- B) A new collection instance
- C) A Boolean indicating success
- D) A
nullobject
- Can immutable collections be used with concurrent programming?
- A) Yes, they are inherently thread-safe
- B) No, they are not supported in concurrency
- C) Only when synchronized manually
- D) Yes, but only with shared locks
3. Basic Operations on Collections
- What does the
mapfunction do in Scala collections?- A) Modifies the collection in place
- B) Applies a function to each element and returns a new collection
- C) Maps keys to values in a
Map - D) Rearranges elements
- Which method is used to combine two collections in Scala?
- A)
merge - B)
concat - C)
++ - D)
combine
- A)
- How do you filter elements in a collection?
- A)
filter(predicate) - B)
select(predicate) - C)
reduce(predicate) - D)
extract(predicate)
- A)
- What does the
foldfunction do?- A) Combines elements using an associative operation
- B) Filters elements based on a condition
- C) Converts a collection to a string
- D) Reverses the collection
- Which method is used to find the first element of a collection?
- A)
first() - B)
get(0) - C)
head - D)
start
- A)
- How do you check if a collection is empty?
- A)
isEmpty - B)
size == 0 - C)
length == 0 - D) All of the above
- A)
- What does the
reducefunction do in a collection?- A) Finds the smallest element
- B) Combines elements into a single value
- C) Filters elements based on a condition
- D) Converts the collection to another type
- Which operation is used to transform a collection into a single result?
- A)
map - B)
reduce - C)
transform - D)
convert
- A)
- How do you reverse a collection?
- A)
reverse() - B)
collection.reverse - C)
collection.invert - D)
collection.flip
- A)
- Which method sorts a collection in ascending order?
- A)
sort() - B)
sorted - C)
sortAsc - D)
arrange
- A)
Answers
| Qno | Answer |
|---|---|
| 1 | B) It maintains insertion order |
| 2 | D) Both A and C |
| 3 | C) It contains unique elements |
| 4 | A) Map(key -> value) |
| 5 | B) A sequence of immutable elements |
| 6 | C) Using .index notation (e.g., .1, .2) |
| 7 | C) 22 |
| 8 | A) List |
| 9 | B) Returns None |
| 10 | D) contains |
| 11 | B) Elements cannot be added, modified, or removed |
| 12 | C) List |
| 13 | A) Set(1, 2, 3) |
| 14 | C) Yes, but it creates a new instance |
| 15 | D) All of the above |
| 16 | A) Adding elements |
| 17 | C) collection.toList |
| 18 | A) They ensure side effects are minimized |
| 19 | B) A new collection instance |
| 20 | A) Yes, they are inherently thread-safe |
| 21 | B) Applies a function to each element and returns a new collection |
| 22 | C) ++ |
| 23 | A) filter(predicate) |
| 24 | A) Combines elements using an associative operation |
| 25 | C) head |
| 26 | D) All of the above |
| 27 | B) Combines elements into a single value |
| 28 | B) reduce |
| 29 | B) collection.reverse |
| 30 | B) sorted |