Sealed classes for restricted hierarchies 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'

AShape

BShapes

Cshape

DshapeClass

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or plural forms for the class name.

The sealed class must be declared with the exact name Shape to match the requirement.

2fill in blank

medium

Complete the code to declare a subclass Circle of the sealed class Shape.

Kotlin

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

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

AshapeClass

Bshape

CShape

DShapes

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect class names or lowercase names for inheritance.

The subclass must inherit from the sealed class Shape using the exact class name.

3fill in blank

hard

Fix the error in the when expression to handle all subclasses of Shape.

Kotlin

fun area(shape: Shape): Double = when(shape) {
    is Circle -> Math.PI * shape.radius * shape.radius
    is Square -> shape.side * shape.side
    [1] -> throw IllegalArgumentException("Unknown shape")
}

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

Adefault

Belse

Cotherwise

Dcatch

Attempts:

3 left

💡 Hint

Common Mistakes

Using invalid keywords like default or catch instead of else.

The when expression requires an else branch to handle all other cases not explicitly matched.

4fill in blank

hard

Fill both blanks to declare a sealed class Shape with two subclasses Circle and Square.

Kotlin

sealed class [1] {
    class Circle(val radius: Double) : [2]()
    class Square(val side: Double) : Shape()
}

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

AShape

Bshape

CShapes

DshapeClass

Attempts:

3 left

💡 Hint

Common Mistakes

Using different or lowercase names for the sealed class or superclass.

Both the sealed class and the superclass in the subclasses must be named Shape exactly.

5fill in blank

hard

Fill all three blanks to create a sealed class Shape with subclasses Circle and Square, and a function to calculate area.

Kotlin

sealed class [1] {
    class Circle(val radius: Double) : [2]()
    class Square(val side: Double) : Shape()
}

fun area(shape: [3]): Double = when(shape) {
    is Circle -> Math.PI * shape.radius * shape.radius
    is Square -> shape.side * shape.side
}

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

AShape

Bshape

DShapes

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent or incorrect class names.

The sealed class and its subclasses must use the exact name Shape. The function parameter type must also be Shape.