An interface with only one abstract method is called a functional interface(Single Abstract Method). functional (SAM) interface can have multiple non abstract method but only one abstract method
// functional interface example
interface CatchAble {
fun invoke()
}
SAM conversions
Instead of creating a class that implements a functional interface manually, you can use a lambda expression.
// functional interface example
interface CatchAble {
fun invoke()
}
// functional interface example
fun interface FunctInterface{
fun invoke(list: List<Int>) :List<Int>
}
// functional interface
interface FuncInterface3 {
fun abstract_method(a: Int, b: String?)
// Second method prevents lambda conversion
fun nonabstract_method() {
println("do something")
}
}
fun main(){
// if we don't use SAM conversion
val run = object : CatchAble {
override fun invoke() {
print("Invoking CatchAble ")
}
}
run.invoke() // // Invoking CatchAble
// if don't SAM use SAM conversion
val fi = object :FunctInterface{
override fun invoke(list: List<Int>): List<Int> {
return list.filter { pre -> pre %2 ==0 }
}
}
print(fi.invoke(listOf(2,5,1,5,79,0))) // [2, 0]
// using same conversion
val fi2 = FunctInterface {
it.filter { pre -> pre %2 == 0 }
}
print(fi2.invoke(listOf(2,5,1,5,79,0))) // [2, 0]
val fi3 = object : FuncInterface3{
override fun abstract_method(a: Int, b: String?) {
print("This is abstract method")
}
// it's not force to override this method
override fun nonabstract_method() {
print("overriding non abstract method")
}
}
fi3.nonabstract_method() // do something
fi3.abstract_method(2,"323") //overriding non-abstract method
}
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