Count words in file

Main.java

package com.kh0ma.demo;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Map;
import java.util.stream.Collectors;

/**
 * @author Oleksandr Khomenko
 */
public class UniqueWords {
    public static final String WHITESPACE_REGEX = "\\s+";
    public static final String NON_WORD_REGEX = "[^\\w]";
    public static final String BLANK_STRING = "";

    public static void main(String[] args) throws IOException {
        Map<String, Integer> result = countUniqueWordsInFile(Paths.get(args[0]));

        result.entrySet().stream()
                .sorted(Comparator.comparing(Map.Entry::getValue))
                .forEach(System.out::println);
    }

    private static Map<String, Integer> countUniqueWordsInFile(Path pathToFile) throws IOException {
        return Files.lines(pathToFile)
                .map(line -> line.split(WHITESPACE_REGEX))
                .flatMap(Arrays::stream)
                .map(w -> w.replaceAll(NON_WORD_REGEX, BLANK_STRING))
                .filter(s -> !s.isEmpty())
                .collect(Collectors.toMap(k -> k, v -> 1, (oldVal, newVal) -> oldVal + newVal));
    }
}