Enum class declaration in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an enum class named Direction.

Kotlin

enum class [1] {
    NORTH, SOUTH, EAST, WEST
}

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

Adirection

BDirection

CEnumDirection

DDirections

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase for the enum class name

Using plural form instead of singular

The enum class name should be Direction with capital D as per Kotlin naming conventions.

2fill in blank

medium

Complete the code to access the enum constant EAST from Direction.

Kotlin

val dir = Direction.[1]

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

Aeast

BeAST

CEast

DEAST

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or mixed case for enum constants

Enum constants in Kotlin are uppercase by convention, so EAST is correct.

3fill in blank

hard

Fix the error in the enum class declaration by completing the blank.

Kotlin

enum [1] Direction {
    NORTH, SOUTH, EAST, WEST
}

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

Aclass

Benumclass

CEnum

Denum_class

Attempts:

3 left

💡 Hint

Common Mistakes

Writing enumclass as one word

Using incorrect keywords like Enum or enum_class

The correct syntax to declare an enum class in Kotlin is enum class.

4fill in blank

hard

Fill both blanks to declare an enum class Color with constants RED and BLUE.

Kotlin

enum [1] [2] {
    RED, BLUE
}

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

Aclass

Bobject

CColor

Dcolor

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase for the class name

Using object instead of class

The correct syntax is enum class Color to declare the enum class.

5fill in blank

hard

Fill all three blanks to create an enum class Weekday with constants MONDAY and FRIDAY.

Kotlin

enum [1] [2] {
    [3], FRIDAY
}

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

Aclass

BWeekday

CMONDAY

Dweekday

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase for class or constant names

Missing the class keyword

The enum class declaration is enum class Weekday and constants are uppercase like MONDAY.

Practice

1. What is the main purpose of an enum class in Kotlin?

easy

A. To define a function that returns multiple values

B. To group a fixed set of related constants under one type

C. To create a class that can be instantiated multiple times

D. To declare a variable that can hold any data type

Solution

1. Step 1: Understand enum class purpose

   An enum class is designed to hold a fixed set of constants that belong together logically.

2. Step 2: Compare options with enum usage

   Only To group a fixed set of related constants under one type correctly describes grouping related constants under one type, which is the main use of enum classes.

3. Final Answer:

   To group a fixed set of related constants under one type -> Option B

4. Quick Check:

   Enum class purpose = group constants [OK]

Hint: Enums group fixed constants for clarity and safety [OK]

Common Mistakes:

• Thinking enums are for creating multiple instances
• Confusing enums with regular classes
• Believing enums can hold any data type variable

2. Which of the following is the correct syntax to declare an enum class named Direction with constants NORTH, SOUTH, EAST, and WEST?

easy

A. enum class Direction { NORTH, SOUTH, EAST, WEST }

B. class enum Direction { NORTH, SOUTH, EAST, WEST }

C. enum Direction { NORTH; SOUTH; EAST; WEST }

D. enum class Direction = (NORTH, SOUTH, EAST, WEST)

Solution

1. Step 1: Recall Kotlin enum class syntax

   Kotlin enum classes start with enum class followed by the name and curly braces containing constants separated by commas.

2. Step 2: Check each option's syntax

   enum class Direction { NORTH, SOUTH, EAST, WEST } matches the correct syntax. Options A, C, and D have incorrect keywords, punctuation, or structure.

3. Final Answer:

   enum class Direction { NORTH, SOUTH, EAST, WEST } -> Option A

4. Quick Check:

   Correct enum syntax = enum class Direction { NORTH, SOUTH, EAST, WEST } [OK]

Hint: Use 'enum class Name { CONST1, CONST2 }' syntax [OK]

Common Mistakes:

• Using 'class enum' instead of 'enum class'
• Separating constants with semicolons instead of commas
• Assigning enum constants with '=' instead of listing

3. What will be the output of the following Kotlin code?

enum class Color { RED, GREEN, BLUE }
fun main() {
    val c = Color.GREEN
    println(c.name)
}

medium

A. green

B. Color.GREEN

C. 1

D. GREEN

Solution

1. Step 1: Understand enum constant property 'name'

   Each enum constant has a built-in name property that returns its exact name as a string.

2. Step 2: Analyze the code output

   The code prints c.name where c is Color.GREEN, so it prints "GREEN" exactly as declared.

3. Final Answer:

   GREEN -> Option D

4. Quick Check:

   Enum constant name property = GREEN [OK]

Hint: Enum.name returns constant name as string [OK]

Common Mistakes:

• Expecting lowercase output
• Printing enum constant directly without .name
• Confusing ordinal number with name

4. Identify the error in this Kotlin enum class declaration:

enum class Size {
    SMALL,
    MEDIUM
    LARGE
}

medium

A. Cannot declare enum class without constructor

B. Enum constants must be lowercase

C. Missing comma after MEDIUM

D. Enum class must have at least 5 constants

Solution

1. Step 1: Check enum constants separation

   Enum constants must be separated by commas except the last one. Here, MEDIUM is missing a comma after it.

2. Step 2: Validate other options

   Constants can be uppercase, no constructor is required, and no minimum count is needed. So only missing comma is the error.

3. Final Answer:

   Missing comma after MEDIUM -> Option C

4. Quick Check:

   Enum constants separated by commas [OK]

Hint: Separate enum constants with commas except last [OK]

Common Mistakes:

• Omitting commas between constants
• Using lowercase for constants (not required)
• Thinking constructor is mandatory

5. How can you add a property rgb to an enum class Color that stores the color's RGB integer value, and access it for Color.RED? Choose the correct code snippet.

hard

A. enum class Color(val rgb: Int) { RED(0xFF0000), GREEN(0x00FF00), BLUE(0x0000FF) }
fun main() { println(Color.RED.rgb) }

B. enum class Color { RED = 0xFF0000, GREEN = 0x00FF00, BLUE = 0x0000FF }
fun main() { println(Color.RED.rgb) }

C. enum class Color { RED(0xFF0000), GREEN(0x00FF00), BLUE(0x0000FF) }
fun main() { println(Color.RED.rgb) }

D. enum class Color { RED, GREEN, BLUE }
fun main() { println(Color.RED.rgb) }

Solution

1. Step 1: Understand enum property declaration

   To add a property, declare a constructor parameter in the enum class and pass values to each constant.

2. Step 2: Check each option for correct syntax

   enum class Color(val rgb: Int) { RED(0xFF0000), GREEN(0x00FF00), BLUE(0x0000FF) } fun main() { println(Color.RED.rgb) } correctly declares val rgb: Int in constructor and assigns values. enum class Color { RED = 0xFF0000, GREEN = 0x00FF00, BLUE = 0x0000FF } fun main() { println(Color.RED.rgb) } uses invalid assignment syntax. enum class Color { RED(0xFF0000), GREEN(0x00FF00), BLUE(0x0000FF) } fun main() { println(Color.RED.rgb) } misses constructor declaration. enum class Color { RED, GREEN, BLUE } fun main() { println(Color.RED.rgb) } has no property defined.

3. Final Answer:

   enum class Color(val rgb: Int) { RED(0xFF0000), GREEN(0x00FF00), BLUE(0x0000FF) } fun main() { println(Color.RED.rgb) } -> Option A

4. Quick Check:

   Enum property via constructor = enum class Color(val rgb: Int) { RED(0xFF0000), GREEN(0x00FF00), BLUE(0x0000FF) } fun main() { println(Color.RED.rgb) } [OK]

Hint: Add properties via constructor parameters in enum class [OK]

Common Mistakes:

• Trying to assign values with '=' inside enum constants
• Not declaring constructor parameters in enum class
• Accessing property that was never declared