Kotlin Academy · Lesson

Using Annotations

Annotate code.

What Are Annotations?

Annotations attach metadata to code. They do not change behavior by themselves, but tools, compilers, and libraries read them to make decisions.

You write an annotation with @ followed by its name, placed right before the element it applies to.

The standard library ships several useful annotations. @Deprecated marks code that should no longer be used and shows a warning at the call site.

@Deprecated("Use newGreet() instead")
fun greet() = "Hi"

fun newGreet() = "Hello"

fun main() {
    println(newGreet())
}