public static void main(String[] args) {

    try (BufferedReader reader = Files.newBufferedReader(

            Paths.get("myfile.txt"),

            StandardCharsets.UTF_8)) {

        System.out.println(reader.lines().count());

    } catch (IOException ex) {

    }

}

Print out all the lines:

 

public static void main(String[] args) {

    try (BufferedReader reader = Files.newBufferedReader(

            Paths.get("myfile.txt"),

            StandardCharsets.UTF_8)) {

        reader.lines().forEach(System.out::println);

    } catch (IOException ex) {

    }

}

Print out the longest line in a file:

 

public static void main(String[] args) {

    try (BufferedReader reader = Files.newBufferedReader(

            Paths.get("myfile.txt"),

            StandardCharsets.UTF_8)) {

        System.out.println(reader

                .lines()

                .mapToInt(String::length)

                .max()

                .getAsInt());

    } catch (IOException ex) {

    }

}