Companion objects as static alternatives in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a companion object inside the class.

Kotlin

class MyClass {
    [1] object {
        fun greet() = "Hello"
    }
}

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

ACompanion

BCompanionObject

Cstatic

Dcompanion

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase 'Companion' instead of lowercase 'companion'.

Trying to use 'static' keyword which does not exist in Kotlin.

In Kotlin, the keyword to declare a companion object is lowercase 'companion'.

2fill in blank

medium

Complete the code to call the greet() function from the companion object.

Kotlin

fun main() {
    println(MyClass.[1]())
}

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

Agreet

BMyClass.greet

Ccompanion.greet

Dgreet()

Attempts:

3 left

💡 Hint

Common Mistakes

Including parentheses inside the blank.

Trying to access 'companion.greet' explicitly.

You call the function directly on the class name followed by the function name without parentheses in the blank.

3fill in blank

hard

Fix the error in the companion object declaration by completing the blank.

Kotlin

class Example {
    companion [1] {
        val number = 42
    }
}

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

Acompanion

BObject

Cobject

Dstatic

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the 'object' keyword.

Using uppercase 'Object' or 'static' keyword.

The correct syntax is 'companion object' with 'object' keyword after 'companion'.

4fill in blank

hard

Fill both blanks to create a companion object with a function that returns a greeting.

Kotlin

class Greeting {
    [1] [2] {
        fun sayHello() = "Hi!"
    }
}

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

Acompanion

Bobject

Cstatic

DCompanion

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'static' keyword which is not valid in Kotlin.

Capitalizing keywords incorrectly.

A companion object is declared with 'companion object' keywords.

5fill in blank

hard

Fill all three blanks to define a companion object with a constant and a function.

Kotlin

class Constants {
    [1] [2] {
        const val PI = 3.14
        fun getPi() = [3]
    }
}

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

Acompanion

Bobject

CPI

Dpi

Attempts:

3 left

💡 Hint

Common Mistakes

Returning 'pi' instead of 'PI' (case sensitive).

Omitting 'object' keyword.

The companion object is declared with 'companion object', and the function returns the constant 'PI'.