LineCount.java

package chapter01;

import java.io.IOException;
import java.nio.file.*;
import java.util.List;
import java.util.stream.Stream;

public class LineCount {
    private final int total;
    private final int empty;

    public LineCount(int total, int empty) {
        this.total = total;
        this.empty = empty;
    }

    private static LineCount countLines(Path path) throws IOException {
        if (Files.isDirectory(path)) return null;
        List<String> lines = Files.readAllLines(path);
        Stream<String> emptyLines = lines.stream().filter(
                (String line) -> line.trim().isEmpty());
        return new LineCount(lines.size(), (int) emptyLines.count());
    }

    public static void main(String[] args) {
        try {
            for (String arg : args) {
                LineCount lineCount = countLines(Paths.get(arg));
                if (lineCount == null) continue;
                System.out.println(arg + ": " + lineCount.total +
                     " total lines, " + lineCount.empty + " empty lines");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

LineCount.kt

package chapter01.linecount

import java.io.File

data class LineCount(val total: Int,
                     val empty: Int)

fun File.countLines(): LineCount? {
    if (isDirectory()) return null
    val lines = readLines()
    val emptyLines = lines.filter { it.trim().isEmpty() }
    return LineCount(lines.size(), emptyLines.size())
}

fun main(args: Array<String>) {
    for (fileName in args) {
        val (total, empty) = File(fileName).countLines() ?: continue
        println("$fileName: $total total lines, $empty empty lines")
    }
}

https://gist.github.com/programaths/505b5eafd8809a93e9a1d9a2dacdf315