enum class

Learn to define named constants with enum class.

enum class: named constants

An enum class defines a fixed set of values. Each constant has a name; a typo is caught at compile time. It is ideal for colors, directions, days of the week.

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

Constants are separated by commas inside braces. To access one, write Color.RED. You use a meaningful name instead of a number, which improves readability.

Accessing an enum constant

To access a constant, write ClassName.CONSTANT. A constant is an object; the name property returns its name.

val r = Color.RED
println(r.name)  // "RED"
println(r)       // RED

Comparing two constants with == is safe; each constant is a single object. name always returns the name as declared. This gives you consistent output in logs or interfaces.

Exercise Define the Signal enum

Define an enum class called Signal with RED, YELLOW, GREEN. In main print the Signal.YELLOW constant with println.

Show example solution

enum class Signal { RED, YELLOW, GREEN }

fun main() {
    println(Signal.YELLOW)
}

Test yourself

What kind of values does an enum class hold?
- Random numbers
- Named constants
- Dynamic text
- File paths
Show answer

Named constants — Each constant has a name; the compiler checks them.
Fill in the blank: enum constant
```
val c = Color.____
```
Show answer
```
val c = Color.RED
```
Match constant to meaning

RED

Red
GREEN

Green
BLUE

Blue
name

Constant name

Next lesson: Enum values

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