Sealed classes with when exhaustive check in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a sealed class named Shape.

Kotlin

sealed class [1]

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

AclassShape

BShape

Cshape

DsealedShape

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or incorrect class names.

Adding extra words to the class name.

The sealed class must be named Shape exactly as intended.

2fill in blank

medium

Complete the code to define a data class Circle inheriting from Shape with a radius property.

Kotlin

data class Circle(val radius: Double) : [1]()

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

AShape

Bshape

CCircle

Dsealed

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'shape' instead of 'Shape'.

Trying to inherit from the same class name.

The class Circle must inherit from the sealed class Shape.

3fill in blank

hard

Fix the error in the when expression to make it exhaustive for Shape.

Kotlin

fun area(shape: Shape): Double = when(shape) {
    is Circle -> Math.PI * shape.radius * shape.radius
    is Rectangle -> shape.width * shape.height
    [1]
}

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

Ais Shape -> 0.0

Bis Square -> shape.side * shape.side

Celse -> 0.0

Dis Triangle -> 0.5 * shape.base * shape.height

Attempts:

3 left

💡 Hint

Common Mistakes

Missing the else branch causing compilation error.

Adding incorrect or incomplete subclass checks.

Adding else makes the when expression exhaustive if not all subclasses are covered.

4fill in blank

hard

Fill both blanks to create a when expression that is exhaustive without else, covering all subclasses.

Kotlin

fun describe(shape: Shape): String = when(shape) {
    is Circle -> "Circle with radius ${shape.radius}"
    [1] -> "Rectangle with width ${shape.width} and height ${shape.height}"
    [2] -> "Square with side ${shape.side}"
}

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

Ais Rectangle

Bis Square

Cis Triangle

Delse

Attempts:

3 left

💡 Hint

Common Mistakes

Using else instead of subclass names.

Missing one subclass causing non-exhaustive error.

To make the when exhaustive without else, all subclasses must be covered explicitly.

5fill in blank

hard

Fill all three blanks to create a sealed class hierarchy and an exhaustive when expression that returns area.

Kotlin

sealed class [1]
data class Circle(val radius: Double) : [1]()
data class Rectangle(val width: Double, val height: Double) : [1]()
fun area(shape: [1]): Double = when(shape) {
    is Circle -> Math.PI * shape.radius * shape.radius
    is Rectangle -> shape.width * shape.height
}

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

AShape

BCircle

CRectangle

Dsealed

Attempts:

3 left

💡 Hint

Common Mistakes

Using different class names in inheritance.

Using 'sealed' keyword instead of class name.

All classes inherit from the sealed class Shape, and the function uses it as parameter type.