import java.util.function.*;
    
    class Example {
        public static int myf(int i, Function<Integer,Integer> fn) {
            System.out.println("start");
            int retval = fn.apply(i);
            System.out.println(retval);
            System.out.println("end");
            return retval;
        }
        public static void main(String[] args) {
            myf(3, i -> i * 10);
            myf(4, i -> i - 10);
        }
    }