Object expressions (anonymous objects) in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an anonymous object with a property name.

Kotlin

val obj = object {
    val [1] = "Kotlin"
}
println(obj.name)

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

Atype

Bvalue

Cname

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different property name like value or type will cause an error when accessing obj.name.

The anonymous object has a property called name, so you must declare it as val name.

2fill in blank

medium

Complete the code to override the toString() method in an anonymous object.

Kotlin

val obj = object {
    override fun [1](): String {
        return "Anonymous Object"
    }
}
println(obj.toString())

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

AtoString

Bequals

ChashCode

Dcopy

Attempts:

3 left

💡 Hint

Common Mistakes

Overriding equals or hashCode instead of toString will not change the printed output.

To customize the string representation, override the toString() method.

3fill in blank

hard

Fix the error in the code by completing the anonymous object declaration that implements the interface Runnable.

Kotlin

val runnable = object : [1] {
    override fun run() {
        println("Running")
    }
}
runnable.run()

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

ACallable

BRunnable

CThread

DExecutor

Attempts:

3 left

💡 Hint

Common Mistakes

Using Callable or Thread instead of Runnable causes type errors.

To create an anonymous object that implements Runnable, use object : Runnable.

4fill in blank

hard

Fill both blanks to create an anonymous object with a property and a method.

Kotlin

val obj = object {
    val [1] = 10
    fun [2]() = [1] * 2
}
println(obj.doubleValue())

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

Avalue

BdoubleValue

Cnumber

Dcalculate

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the property or method than those called causes errors.

The property is named value and the method is doubleValue which returns twice the property.

5fill in blank

hard

Fill all three blanks to create an anonymous object that implements an interface and overrides a method.

Kotlin

interface Greeter {
    fun greet(): String
}

val greeter = object : [1] {
    override fun [2]() = "Hello, [3]!"
}
println(greeter.greet())

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

AGreeter

Bgreet

CWorld

DGreeting

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong interface or method names causes compilation errors.

The anonymous object implements Greeter, overrides greet(), and returns "Hello, World!".