Collections interop behavior in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Kotlin list from a Java list.

Kotlin

val javaList = java.util.ArrayList<String>()
javaList.add("apple")
val kotlinList: List<String> = [1](javaList)

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AArrayList

BlistOf

CmutableListOf

DCollections

Attempts:

3 left

💡 Hint

Common Mistakes

Using listOf() which creates an immutable list and does not accept a Java list directly.

Using mutableListOf() which creates an empty list.

Use ArrayList(javaList) to create a Kotlin list from a Java list.

2fill in blank

medium

Complete the code to convert a Kotlin list to a Java list.

Kotlin

val kotlinList = listOf("one", "two", "three")
val javaList: java.util.List<String> = kotlinList.[1]()

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AtoCollection

BtoMutableList

CtoList

DtoJavaList

Attempts:

3 left

💡 Hint

Common Mistakes

Using toList() which returns an immutable Kotlin list, not a Java list.

Using toJavaList() which does not exist.

Use toMutableList() to get a Java mutable list from a Kotlin list.

3fill in blank

hard

Fix the error in the code to add an element to a Java list obtained from a Kotlin list.

Kotlin

val kotlinList = listOf("a", "b")
val javaList: java.util.List<String> = kotlinList.[1]()
javaList.add("c")

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AtoList

BtoSet

CasList

DtoMutableList

Attempts:

3 left

💡 Hint

Common Mistakes

Using toList() which returns an immutable list causing add() to fail.

Using asList() which returns a fixed-size list.

Use toMutableList() to get a mutable Java list that supports adding elements.

4fill in blank

hard

Fill both blanks to create a Kotlin map from a Java map and access a value.

Kotlin

val javaMap = java.util.HashMap<String, Int>()
javaMap["x"] = 10
val kotlinMap: Map<String, Int> = [1](javaMap)
val value = kotlinMap[[2]]

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AHashMap

B"x"

CmapOf

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using mapOf() which creates an empty map here.

Using 10 as a key instead of "x".

Use HashMap(javaMap) to create a Kotlin map from a Java map, and access the value with the key "x".

5fill in blank

hard

Fill all three blanks to filter a Kotlin list converted from a Java list.

Kotlin

val javaList = java.util.ArrayList<Int>()
javaList.add(1)
javaList.add(2)
javaList.add(3)
val kotlinList = [1](javaList)
val filtered = kotlinList.filter { it [2] [3] }

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AArrayList

B>

C1

DlistOf

Attempts:

3 left

💡 Hint

Common Mistakes

Using listOf which creates an immutable list.

Using '<' instead of '>' in the filter.

Convert the Java list to a Kotlin ArrayList, then filter elements greater than 1.