Elvis operator deep usage in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign a default value using the Elvis operator.

Kotlin

val name: String? = null
val displayName = name [1] "Unknown"

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

A?.

B==

C!!

D?:

Attempts:

3 left

💡 Hint

Common Mistakes

Using !! instead of ?: causes a crash if the value is null.

Using ?. only safely accesses properties but doesn't provide a default.

The Elvis operator ?: returns the left value if it's not null, otherwise the right value.

2fill in blank

medium

Complete the code to safely get the length of a nullable string or return 0 using the Elvis operator.

Kotlin

val text: String? = null
val length = text?.length [1] 0

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

A?:

B?.

C!!

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using !! causes an exception if text is null.

Using == is a comparison, not a fallback.

The Elvis operator ?: returns 0 if text?.length is null.

3fill in blank

hard

Fix the error in the code by completing the Elvis operator usage to provide a default value.

Kotlin

fun getUserName(user: User?): String {
    return user?.name [1] "Guest"
}

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

A!!

B?:

C?.

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using !! causes a crash if user or name is null.

Using ?. does not provide a default value.

Use ?: to return "Guest" if user?.name is null.

4fill in blank

hard

Fill both blanks to use the Elvis operator and safe call to get the length or return -1.

Kotlin

fun getLength(str: String?): Int {
    return str[1]length [2] -1
}

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

A?.

B?:

C!!

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using !! can cause exceptions if str is null.

Using == is a comparison, not a fallback.

Use ?. to safely access length and ?: to provide -1 if null.

5fill in blank

hard

Fill all three blanks to chain safe calls and Elvis operators to get a nested property or default.

Kotlin

fun getCountry(user: User?): String {
    return user[1]address[2]country [3] "Unknown"
}

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

A?.

B?:

C!!

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using !! can cause crashes if any property is null.

Using == is a comparison, not a fallback.

Use ?. to safely access nested properties and ?: to provide a default.