Type inference by the compiler in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a variable with type inferred by the compiler.

Kotlin

val number = [1]

Drag options to blanks, or click blank then click option'

Atrue

B"Hello"

C3.14

D42

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string or boolean value when an integer is expected.

The compiler infers the type of number as Int because the value 42 is an integer.

2fill in blank

medium

Complete the code to declare a variable with type inferred as String.

Kotlin

val greeting = [1]

Drag options to blanks, or click blank then click option'

A"Welcome"

B100

Cfalse

D2.718

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a number or boolean instead of a string.

The compiler infers the type of greeting as String because the value is a text inside quotes.

3fill in blank

hard

Fix the error by completing the code to declare a variable with type inferred as Boolean.

Kotlin

val isActive = [1]

Drag options to blanks, or click blank then click option'

Atrue

B"true"

C1

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string "true" instead of boolean true.

Using numbers or null instead of boolean.

The compiler infers isActive as Boolean because the value true is a boolean literal, not a string.

4fill in blank

hard

Fill both blanks to create a list with type inferred by the compiler.

Kotlin

val numbers = listOf([1], [2])

Drag options to blanks, or click blank then click option'

A1

B"two"

C3

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing types like string and integer in the list elements.

The list contains integers 1 and 3, so the compiler infers the list type as List<Int>.

5fill in blank

hard

Fill all three blanks to create a map with type inferred by the compiler.

Kotlin

val map = mapOf([1] to [2], [3] to 42)

Drag options to blanks, or click blank then click option'

A"one"

B1

C"two"

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using integers as keys and strings as values inconsistently.

The map has keys as strings "one" and "two", and values as integers 1 and 42. The compiler infers the type as Map<String, Int>.