Kotlin by Example: Enum classes
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A simple enum can be be defined concisely. |
enum class Direction {
NORTH, SOUTH, WEST, EAST
}
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It is also possible to have enum classes with properties and constructors. |
enum class Color(val rgb: Int) {
RED(0xFF0000),
GREEN(0x00FF00),
BLUE(0x0000FF)
}
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It is also possible to add computed properties or methods. The list of enums must be separated from the members with a semicolon. |
enum class BetterColor(val rgb: Int) {
RED(0xFF0000),
GREEN(0x00FF00),
BLUE(0x0000FF);
val r = rgb shr 16;
val g = (rgb shr 8) and 0xff;
val b = rgb and 0xff;
}
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Another more advanced variant is to implement the members as instances of anonymous classes. |
enum class ProtocolState {
WAITING {
override fun signal() = TALKING
},
TALKING {
override fun signal() = WAITING
};
abstract fun signal(): ProtocolState
}
fun main() {
val north = Direction.NORTH
println(north)
val red = Color.RED
println(red)
println(red.rgb)
val moreRed = BetterColor.RED
println(moreRed)
println(moreRed.r)
println(moreRed.g)
println(moreRed.b)
var ps = ProtocolState.WAITING
println(ps)
ps = ps.signal()
println(ps)
ps = ps.signal()
println(ps)
}
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$ kotlinc main.kt -include-runtime -d main.jar
$ java -jar Main.jar
NORTH
RED
16711680
RED
255
0
0
WAITING
TALKING
WAITING
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