package basic; import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; public class StreamB { public interface Foo { int m(int n); } public static void main(String[] args) { System.out.println("This is Java8"); } public static int run() { Foo foo = (n) -> n + 1; List<Integer> integers = Arrays.asList(1, 2, 3); List<Integer> mapped = integers.stream().map(foo::m).collect(Collectors.toList()); return mapped.size(); } }