Safe casts with as? in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to safely cast 'obj' to String using 'as?'.

Kotlin

val str = obj [1] String

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

Aas

Bis

Cas?

Dto

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'as' which throws an exception if the cast fails.

Using 'is' which checks type but does not cast.

Using 'to' which is not a cast operator.

The safe cast operator as? tries to cast the object and returns null if it fails, avoiding exceptions.

2fill in blank

medium

Complete the code to safely cast 'item' to Int and assign to 'number'.

Kotlin

val number: Int? = item [1] Int

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

Aas?

Bis

Cas

Dto

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'as' which throws an exception if cast fails.

Using 'is' which only checks type but does not cast.

Using 'to' which is not a cast operator.

Using as? safely casts 'item' to Int or returns null if it cannot be cast.

3fill in blank

hard

Fix the error in the code by replacing the cast operator with a safe cast.

Kotlin

val text = data [1] String

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

Aas?

Bis

Cas

Dto

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'as' which throws exceptions on failure.

Using 'is' which does not cast but only checks type.

Replacing as with as? prevents exceptions by returning null if the cast fails.

4fill in blank

hard

Fill both blanks to create a safe cast and check if the result is null.

Kotlin

val result = value [1] String
if (result [2] null) {
    println("Cast succeeded")
}

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

Aas?

B==

C!=

Das

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'as' instead of 'as?' causing exceptions.

Using '==' instead of '!=' to check for null.

Use as? for safe cast and != to check if the cast did not return null.

5fill in blank

hard

Fill all three blanks to safely cast 'input' to Double, check if not null, and print the value.

Kotlin

val number = input [1] Double
if (number [2] null) {
    println("Number is: [3]")
}

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

Aas?

B!=

Cnumber

Das

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'as' instead of 'as?'.

Checking '==' null instead of '!=' null.

Printing a wrong variable name.

Use as? for safe cast, != to check not null, and print the variable number.