Flow operators (map, filter, transform) in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to transform each number by doubling it using the map operator.

Kotlin

val numbers = flowOf(1, 2, 3)
val doubled = numbers.[1] { it * 2 }

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

Afilter

Bcollect

Ctransform

Dmap

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter instead of map will only select elements, not transform them.

Using collect is for consuming the flow, not transforming it.

The map operator applies a transformation to each element in the flow.

2fill in blank

medium

Complete the code to keep only even numbers using the filter operator.

Kotlin

val numbers = flowOf(1, 2, 3, 4)
val evens = numbers.[1] { it % 2 == 0 }

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

Amap

Bfilter

Ctransform

Dcollect

Attempts:

3 left

💡 Hint

Common Mistakes

Using map will transform elements but not filter them.

Using collect is for consuming the flow, not filtering.

The filter operator keeps only elements that satisfy the condition.

3fill in blank

hard

Fix the error in the code to emit both original and doubled values using transform.

Kotlin

val numbers = flowOf(1, 2)
val result = numbers.[1] { emit(it); emit(it * 2) }

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

Atransform

Bfilter

Ccollect

Dmap

Attempts:

3 left

💡 Hint

Common Mistakes

Using map only emits one value per input.

Using filter does not emit new values, only filters existing ones.

The transform operator allows emitting multiple values per input.

4fill in blank

hard

Fill both blanks to create a flow of squares of odd numbers.

Kotlin

val numbers = flowOf(1, 2, 3, 4, 5)
val squaresOfOdds = numbers.[1] { it % 2 != 0 }.[2] { it * it }

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

Afilter

Bmap

Ctransform

Dcollect

Attempts:

3 left

💡 Hint

Common Mistakes

Using map before filter will square all numbers before filtering.

Using transform instead of map for simple transformation is more complex.

First, filter keeps odd numbers, then map squares them.

5fill in blank

hard

Fill all three blanks to emit strings for numbers greater than 2, doubled and converted to string.

Kotlin

val numbers = flowOf(1, 2, 3, 4)
val result = numbers.[1] { it [2] 2 }.[3] { (it * 2).toString() }

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

Afilter

B>

Cmap

Dtransform

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' will select wrong numbers.

Using transform instead of map for simple transformation is unnecessary.

Filter numbers greater than 2, then map to double and convert to string.