package basic; import java.util.ArrayList; import java.util.List; import java.util.Map; import java.util.function.Function; import java.util.stream.Collectors; public class LambdaM2 { public static void main(String[] args) { run(); } public static String run() { return new LambdaM2().run2(); } public String run2() { List<String> list = new ArrayList<>(); list.add("test3"); Map m = list.stream().collect(Collectors.toMap(this::foo, Function.identity())); return m.toString(); } public int foo(String input) { return input.length()*2; } }