Why generics provide type safety in Kotlin - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a generic class that holds a value of any type.

Kotlin

class Box<[1]>(val value: T)

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AType

BAny

CT

DValue

Attempts:

3 left

💡 Hint

Common Mistakes

Using a concrete type like Any instead of a generic parameter.

The generic type parameter is declared using T inside angle brackets.

2fill in blank

medium

Complete the function signature to make it generic over type T.

Kotlin

fun <[1]> printValue(value: T) { println(value) }

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AT

BValue

CAny

DType

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to declare the generic type parameter.

Generic functions declare their type parameter before the function name using <T>.

3fill in blank

hard

Fix the error by specifying the correct generic type in the list declaration.

Kotlin

val numbers: List<[1]> = listOf(1, 2, 3)

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ANumber

BString

CAny

DInt

Attempts:

3 left

💡 Hint

Common Mistakes

Using String or Any which do not match the list elements.

The list contains integers, so the generic type must be Int for type safety.

4fill in blank

hard

Fill both blanks to create a generic function that returns the first element of a list.

Kotlin

fun <[1]> firstElement(list: List<[2]>): [1]? = list.firstOrNull()

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AT

BInt

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using different types for the list and return value.

The function uses the same generic type T for the parameter and return type to ensure type safety.

5fill in blank

hard

Fill all three blanks to create a generic class with a method that returns the stored value.

Kotlin

class Container<[1]>(private val item: [2]) {
    fun getItem(): [3] = item
}

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AT

DAny

Attempts:

3 left

💡 Hint

Common Mistakes

Using different types for the property and return type.

The generic type T is used consistently to ensure the class stores and returns the same type safely.