Erro no stream

package br.com.robson.cap9;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Mapa {
    public static void main(String[] args) throws IOException {
        Map<Path, Long> map =
                Files.lines(Paths.get("/home/robson/IdeaProjects/Java8/src/br/com/robson/cap7"))
                .filter( p -> p.endsWith(".java"))
                .collect(Collectors.toMap(
                        Function.identity(),
                        p -> lines(p).count() )); //ta acusando erro nessa linha 

        System.out.println(map);

    }

    static Stream<String> lines(Path p) {
        try {
            return Files.lines(p);
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    }
}