Enum values

Learn to access enum members and their values.

Enum values: entries, valueOf, ordinal

entries returns all constants as a list. valueOf("NAME") goes from name to constant. ordinal gives the declaration order of a constant.

val list = Color.entries  // [RED, GREEN, BLUE]
val c = Color.valueOf("RED")
println(c.ordinal)  // 0

entries is the preferred way in Kotlin 2.x; it is an immutable list. valueOf throws on an unknown name; the name must be exact. ordinal starts at 0 and grows with declaration order.

entries vs values

In Kotlin 2.x entries is preferred; it returns an immutable List. The old values() builds a new array on every call.

val a = Color.entries   // List<Color>
val b = Color.values()  // Array<Color>

entries shares the same list every time; it is more efficient. values() appears in old code; use entries in new code. Both return constants in declaration order.

Exercise Print constants with their ordinals

Define an enum class called Size with SMALL, MEDIUM, LARGE. Loop over entries and print each constant's name and ordinal.

Show example solution

enum class Size { SMALL, MEDIUM, LARGE }

fun main() {
    for (s in Size.entries) {
        println("${s.name} ${s.ordinal}")
    }
}

Test yourself

Match method to job

entries

All constants
valueOf

Find by name
ordinal

Order number
name

Constant name

Fill in the blank: name to constant

val c = Color.____("RED")

Show answer

val c = Color.valueOf("RED")

What does Color.GREEN.ordinal return? (Color: RED, GREEN, BLUE)
- The constant name
- Total count
- The order index
- The color value
Show answer

The order index — ordinal gives the declaration order; GREEN is 1.

Next lesson: Enum properties

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