MCQs on Basic Syntax and Data Types | Scala

200+ Free Scala MCQs Quiz | Basics | MCQs on Scala MCQs on Basic Syntax and Data Types | Scala

Test your knowledge of Scala’s core concepts, including values, variables, constants, primitive types, string operations, and type inference, with these 30 carefully designed multiple-choice questions.

Basic Syntax and Data Types in Scala

1. Values, Variables, and Constants

Which keyword is used to define immutable variables in Scala?
- A) var
- B) val
- C) const
- D) final
What happens if you try to reassign a val variable in Scala?
- A) It overwrites the value
- B) It throws a compilation error
- C) It creates a new instance
- D) It works the same as var
Which keyword is used to define mutable variables in Scala?
- A) val
- B) let
- C) var
- D) const
What is the default value of an uninitialized var in Scala?
- A) 0
- B) null
- C) Depends on the type
- D) No default value; Scala doesn’t allow uninitialized vars
How do you declare a constant in Scala?
- A) const
- B) val
- C) immutable
- D) constant

2. Primitive Data Types

What is the default numeric data type in Scala for a literal like 123?
- A) Int
- B) Long
- C) Float
- D) Double
Which data type in Scala is used to represent a single character?
- A) char
- B) String
- C) Character
- D) Char
How do you define a floating-point literal in Scala?
- A) Append an f or F to the number
- B) Append an l or L to the number
- C) Use a decimal point only
- D) Use double quotes around the number
What is the default size of an Int in Scala?
- A) 16 bits
- B) 32 bits
- C) 64 bits
- D) Platform-dependent
Which of the following is NOT a valid Scala numeric type?
- A) Short
- B) Byte
- C) Decimal
- D) Double

3. String Operations

How do you concatenate two strings in Scala?
- A) Use the + operator
- B) Use the concat() method
- C) Use string interpolation
- D) All of the above
What does the following Scala code output: println("Scala".length)?
- A) 4
- B) 5
- C) 6
- D) An error
What is string interpolation in Scala?
- A) Combining two strings using a separator
- B) Embedding variables in a string using $
- C) Splitting strings into substrings
- D) Removing white spaces from a string
Which method checks if a string contains a specific substring in Scala?
- A) search()
- B) find()
- C) contains()
- D) matches()
Which is a valid way to create a multiline string in Scala?
- A) Use triple double quotes (""")
- B) Use single quotes (''')
- C) Use brackets ({{ }})
- D) Use a backslash at the end of each line

4. Type Inference

What does type inference in Scala allow you to do?
- A) Skip declaring the type explicitly
- B) Define variables without initializing them
- C) Use variables of multiple types
- D) Avoid type checking
What is the inferred type of val x = 10 in Scala?
- A) Double
- B) Int
- C) Float
- D) Long
Which function can you use to explicitly check the type of a value in Scala?
- A) getType()
- B) typeOf()
- C) type()
- D) getClass()
Can Scala infer the return type of a function?
- A) Yes, always
- B) No, it must be explicitly defined
- C) Yes, except for recursive functions
- D) Only for void functions
What happens if a Scala variable type is incorrectly inferred?
- A) The program throws a runtime error
- B) The program throws a compile-time error
- C) The program runs with warnings
- D) This cannot happen; Scala ensures type safety

General Questions

Which of the following is a valid variable declaration in Scala?
- A) var x: Int = 10
- B) val x = 10
- C) var x = "Hello"
- D) All of the above
What is the result of val x = "5" + 2?
- A) 7
- B) 52
- C) Error
- D) “5 2”
Can a var in Scala hold different types of values during its lifecycle?
- A) Yes, always
- B) No, its type is fixed
- C) Yes, only if it’s explicitly mutable
- D) Yes, in REPL only
Which statement about type inference is true?
- A) It only works with val
- B) It only works with var
- C) It works with both val and var
- D) It does not work with uninitialized variables
How do you explicitly define the type of a variable?
- A) Append a : and the type name to the variable
- B) Use as followed by the type name
- C) Declare the variable in a specific block
- D) You cannot explicitly define types in Scala
What happens if you initialize a variable with null in Scala?
- A) It infers the type as Any
- B) It throws a compile-time error
- C) It infers the type as Null
- D) It infers the type as Nothing
Can Scala perform type inference for collections?
- A) No, collection types must always be defined explicitly
- B) Yes, Scala infers the type from the elements
- C) Yes, but only for Lists
- D) Yes, but only for immutable collections
What is the inferred type of an empty list List() in Scala?
- A) List[Any]
- B) List[Int]
- C) List[Nothing]
- D) None
Which Scala feature helps ensure type safety at compile time?
- A) Type inference
- B) Implicits
- C) Case classes
- D) Traits
How can you override type inference in Scala?
- A) By explicitly specifying the type
- B) By redefining the variable
- C) By using the asInstanceOf method
- D) You cannot override type inference

Answers

Qno	Answer
1	B) val
2	B) It throws a compilation error
3	C) var
4	D) No default value; Scala doesn’t allow uninitialized vars
5	B) val
6	A) Int
7	D) Char
8	A) Append an `f` or `F` to the number
9	B) 32 bits
10	C) Decimal
11	D) All of the above
12	B) 5
13	B) Embedding variables in a string using `$`
14	C) contains()
15	A) Use triple double quotes (`"""`)
16	A) Skip declaring the type explicitly
17	B) Int
18	D) getClass()
19	C) Yes, except for recursive functions
20	D) This cannot happen; Scala ensures type safety
21	D) All of the above
22	B) 52
23	B) No, its type is fixed
24	C) It works with both `val` and `var`
25	A) Append a `:` and the type name to the variable
26	C) It infers the type as `Null`
27	B) Yes, Scala infers the type from the elements
28	C) List[Nothing]
29	A) Type inference
30	A) By explicitly specifying the type

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