Enum class declaration in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of enum property access

What is the output of this Kotlin code?

Kotlin

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

fun main() {
    val dir = Direction.EAST
    println(dir.name)
}

A EAST

B Direction.EAST

C Error: Cannot access enum property

D east

💡 Hint

The 'name' property of an enum returns the exact name as declared.

In Kotlin, each enum constant has a 'name' property that returns its name as a string exactly as declared, including case.

❓ Predict Output

intermediate

Enum ordinal value output

What will this Kotlin program print?

Kotlin

enum class Color {
    RED, GREEN, BLUE
}

fun main() {
    println(Color.GREEN.ordinal)
}

A Error: ordinal not accessible

B 2

C 0

D 1

💡 Hint

Ordinal starts counting from zero for the first enum constant.

The 'ordinal' property returns the position of the enum constant starting at 0. RED=0, GREEN=1, BLUE=2.

🔧 Debug

advanced

Identify the error in enum constructor usage

Which option correctly fixes the error in this Kotlin enum declaration?

Kotlin

enum class Size(val cm: Int) {
    SMALL(30), MEDIUM, LARGE(50)
}

A Add a constructor argument to MEDIUM: MEDIUM(40)

B Remove constructor arguments from all constants

C Change val cm to var cm

D Add default value to constructor: val cm: Int = 0

💡 Hint

All enum constants must provide constructor arguments if the enum class has a constructor.

When an enum class has a constructor, all constants must call it with appropriate arguments. MEDIUM lacks an argument causing a compile error.

🧠 Conceptual

advanced

Behavior of enum with overridden methods

What will this Kotlin code print when run?

Kotlin

enum class Mood {
    HAPPY {
        override fun feeling() = "Joy"
    },
    SAD {
        override fun feeling() = "Tears"
    };
    abstract fun feeling(): String
}

fun main() {
    println(Mood.HAPPY.feeling())
    println(Mood.SAD.feeling())
}

A HAPPY\nSAD

B feeling\nfeeling

C Joy\nTears

D Error: abstract method not implemented

💡 Hint

Each enum constant can override abstract methods individually.

The enum declares an abstract method 'feeling'. Each constant overrides it with its own implementation, so the calls print their respective strings.

❓ Predict Output

expert

Output of enum with companion object and custom method

What is the output of this Kotlin program?

Kotlin

enum class Level(val code: Int) {
    LOW(1), MEDIUM(5), HIGH(10);

    companion object {
        fun fromCode(code: Int) = values().find { it.code == code } ?: LOW
    }
}

fun main() {
    println(Level.fromCode(5))
    println(Level.fromCode(7))
}

A MEDIUM\nnull

B MEDIUM\nLOW

C 5\n1

D Error: companion object method not accessible

💡 Hint

The method returns LOW if no matching code is found.

The 'fromCode' method searches for a Level with matching code. 5 matches MEDIUM, 7 matches none so returns LOW by default.