Why object declarations create singletons in Kotlin - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a singleton object named Logger.

Kotlin

object [1] {
    fun log(message: String) {
        println(message)
    }
}

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

Alogger

BLog

CLogger

DLogObject

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase names for object declarations.

Trying to declare an object with class keyword.

The keyword object followed by the name Logger declares a singleton object in Kotlin.

2fill in blank

medium

Complete the code to call the log function on the singleton object.

Kotlin

fun main() {
    [1].log("Hello Singleton")
}

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ALogger

BLogger()

Cnew Logger()

Dlogger

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to create an instance with parentheses.

Using lowercase name that does not match the object.

Singleton objects are accessed by their name directly without parentheses.

3fill in blank

hard

Fix the error in the code to ensure only one instance of the object is used.

Kotlin

val logger1 = [1]
val logger2 = Logger
println(logger1 === logger2)

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ALogger()

Blogger

Cnew Logger()

DLogger

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses to create new instances.

Using lowercase names that do not match the object.

Singleton objects in Kotlin do not use parentheses. Using Logger accesses the single instance.

4fill in blank

hard

Fill both blanks to create a singleton object with a property and access it.

Kotlin

object [1] {
    val version = [2]
}
fun main() {
    println(AppInfo.version)
}

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AAppInfo

B"1.0"

C1.0

DVersion

Attempts:

3 left

💡 Hint

Common Mistakes

Using a number without quotes for a string property.

Using lowercase or incorrect object names.

The object name is AppInfo and the property version is a string "1.0".

5fill in blank

hard

Fill all three blanks to define a singleton object with a function and call it.

Kotlin

object [1] {
    fun greet(name: String) = "Hello, [2]!"
}
fun main() {
    println(Greeter.greet([3]))
}

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

AGreeter

B$name

C"Alice"

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using \$name instead of $name for string interpolation.

Passing a variable name instead of a string literal.

The object is named Greeter. The function uses string interpolation with $name. The call passes the string "Alice".