Generic class declaration in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a generic class named Box.

Kotlin

class Box<[1]> {
    var value: T? = null
}

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AT

BInt

CString

DAny

Attempts:

3 left

💡 Hint

Common Mistakes

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

Forgetting the angle brackets <> around the generic type.

The generic type parameter is declared inside angle brackets after the class name. Here, T is the placeholder for any type.

2fill in blank

medium

Complete the code to create an instance of the generic class Box with type String.

Kotlin

val box: Box<[1]> = Box()

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AInt

BString

CDouble

DBoolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using the generic type parameter T instead of a concrete type.

Omitting the type argument when creating the instance.

To create a Box that holds Strings, specify String as the type argument.

3fill in blank

hard

Fix the error in the generic class declaration by completing the blank.

Kotlin

class Container<[1]> {
    fun getValue(): T? = null
}

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AData

Bvalue

CT

DType

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name instead of a type parameter.

Mismatch between the declared type parameter and its usage.

The generic type parameter must be declared as T to match its usage inside the class.

4fill in blank

hard

Fill both blanks to declare a generic class Pair with two type parameters.

Kotlin

class Pair<[1], [2]> {
    var first: A? = null
    var second: B? = null
}

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

AA

BT

CB

DK

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same letter for both type parameters.

Mismatch between type parameter names and property types.

The class uses two generic type parameters named A and B to represent the types of the two values.

5fill in blank

hard

Fill all three blanks to declare a generic class Triple with three type parameters and properties.

Kotlin

class Triple<[1], [2], [3]> {
    var first: X? = null
    var second: Y? = null
    var third: Z? = null
}

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

AX

BY

CZ

DT

Attempts:

3 left

💡 Hint

Common Mistakes

Using fewer or duplicate type parameters.

Mismatch between type parameters and property types.

The class declares three generic type parameters X, Y, and Z matching the property types.