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100+ Free Kotlin Professional Certificate Practice Questions

Kotlin Professional Certificate by JetBrains practice questions are available now; exam metadata is being verified.

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Which coroutine builder launches a fire-and-forget coroutine and returns a `Job`?

A
B
C
D
to track
2026 Statistics

Key Facts: Kotlin Professional Certificate Exam

4 courses

Courses in the certificate path

JetBrains / LinkedIn Learning

~11 hours

Total course content

JetBrains

April 2026

Certificate launch

The Kotlin Blog

No fee

Included with LinkedIn Premium access

JetBrains / LinkedIn Learning

No expiration

Credential validity

JetBrains

Final exam

Earned by passing a graded assessment after 4 courses

JetBrains

The Kotlin Professional Certificate by JetBrains is a four-course path on LinkedIn Learning (launched April 2026) earned by completing about 11 hours of content and passing a graded final exam. It covers Kotlin essentials, object-oriented and functional Kotlin, coroutines and asynchronous programming, Kotlin Multiplatform, and full-stack/backend basics with Ktor. Access is included with LinkedIn Premium (one-month free trial for eligible users); JetBrains does not publish a fixed question count or numeric passing score, and the certificate does not expire.

Sample Kotlin Professional Certificate Practice Questions

Try these sample questions to test your Kotlin Professional Certificate exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which keyword declares a read-only (immutable) reference in Kotlin?
A.var
B.const
C.val
D.let
Explanation: `val` declares a read-only reference: it must be assigned once and cannot be reassigned. `var` declares a mutable reference that can be reassigned. Preferring `val` is a core Kotlin idiom for safer, more predictable code.
2What does the following code print? val name: String? = null println(name?.length ?: -1)
A.-1
B.0
C.null
D.It throws a NullPointerException
Explanation: The safe-call operator `?.` returns null when `name` is null instead of throwing. The Elvis operator `?:` then substitutes the right-hand value, so the expression evaluates to -1 and that is printed.
3In Kotlin, what is the type of the expression `if (x > 0) "pos" else "neg"`?
A.String, because if is an expression that returns a value
B.Unit, because if is a statement
C.Boolean
D.Any, because the branches differ
Explanation: In Kotlin `if` is an expression, not just a statement, so it produces a value. Because both branches yield String literals, the whole expression has type String and can be assigned directly to a variable.
4Which statement about Kotlin's `String` template syntax is correct for the variable `count`?
A."Total: %count%" interpolates the value of count
B."Total: #{count}" interpolates the value of count
C."Total: @count" interpolates the value of count
D."Total: ${count}" interpolates the value of count
Explanation: Kotlin string templates use the dollar sign: `$count` for a simple variable and `${expression}` for an arbitrary expression. So `"Total: ${count}"` embeds the value of `count` in the string.
5What is printed by this code? val list = listOf(1, 2, 3) val result = list.map { it * 2 } println(result)
A.[2, 4, 6]
B.[1, 2, 3]
C.[1, 4, 9]
D.6
Explanation: `map` transforms each element using the lambda and returns a new list. The lambda `{ it * 2 }` doubles each element, producing [2, 4, 6]. The implicit `it` parameter refers to the current element.
6Which declaration makes `age` a mutable property that starts at 0?
A.var age = 0
B.val age = 0
C.const age = 0
D.let age = 0
Explanation: `var age = 0` declares a mutable property initialized to 0; its type Int is inferred and it can be reassigned later. Use `var` only when reassignment is genuinely needed.
7What does the `!!` (non-null assertion) operator do?
A.Returns null silently if the value is null
B.Throws a NullPointerException if the value is null, otherwise returns the non-null value
C.Converts a non-null type to a nullable type
D.Provides a default value when the receiver is null
Explanation: The `!!` operator converts a nullable value to its non-null type, but if the value is actually null it throws a KotlinNullPointerException at that point. It should be used sparingly because it bypasses Kotlin's null-safety guarantees.
8How is a function that takes two Int parameters and returns their sum declared in Kotlin?
A.fun sum(a: Int, b: Int): Int { return a + b }
B.int sum(int a, int b) { return a + b; }
C.func sum(a Int, b Int) Int { return a + b }
D.def sum(a: Int, b: Int) -> Int: return a + b
Explanation: Kotlin functions use the `fun` keyword, parameters are written `name: Type`, and the return type follows the parameter list after a colon. `fun sum(a: Int, b: Int): Int { return a + b }` is the correct form.
9What does this single-expression function return when called as `square(4)`? fun square(n: Int) = n * n
A.16
B.8
C.Unit
D.It does not compile without a return type
Explanation: This is an expression-body function: the `=` form lets Kotlin infer the return type from the expression. `4 * 4` is 16, so `square(4)` returns 16. No explicit `return` or return type is required here.
10What is printed? val x = 5 val label = when { x < 0 -> "negative" x == 0 -> "zero" else -> "positive" } println(label)
A.positive
B.zero
C.negative
D.Nothing, because when needs a subject
Explanation: A `when` without a subject evaluates each branch condition as a Boolean. With x = 5, the first two conditions are false, so the `else` branch runs and assigns "positive". `when` is an expression, so its value is stored in `label`.

About the Kotlin Professional Certificate Practice Questions

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