@FunctionalInterface
interface Interf {
fun m1(num: Int)
}
fun main() {
val a: Interf = { 34 -> println("Hello world !!") }
}
Upon compilation getting this error
Unexpected tokens (use ';' to separate expressions on the same line)
Is Kotlin lambda function syntax is bit different from Java Lambda Expression?
First of all, this will not compile in java as well:
@FunctionalInterface
interface Interf {
void m1(int num);
}
class Main {
public static void main(String[] args) {
Interf f = 34 -> System.out.println("Hello world !!"); //compilation error here
}
}
With pretty the same error:
error: ';' expected
Interf f = 34 -> System.out.println("Hello world !!");
^
To make it correct, name of the lambda parameter should be changed, so that it become a valid java identifier.
For instance, this will compile:
Interf f = x -> System.out.println("Hello world !!");
Now, returning back to Kotlin. Version 1.4 introduces syntax for SAM conversions:
fun interface Interf {
fun m1(num: Int)
}
It could be instantiated with:
val a = Interf { println("Hello world !!") }
Convention of implicitly declared it parameter referring to lambda only parameter is preserved here.
reason why it's not working for Shivam is because he must use an argument e.g. x instead of 34 as in val a: Interf = { x -> println("Hello world !!") }. This is because he needs to provide an argument, not apply an argument!
val a = { num: Int -> println("Hello World") } a.invoke(2). Here a.invoke(int) or a(int) both can be used.