How to count words in a text file, java 8-style

问题

I'm trying to perform an assignment that first counts the number of files in a directory and then give a word count within each file. I got the file count alright, but I'm having a hard time converting some code my instructor gave me from a class that does a frequency count to the simpler word count. Moreover, I can't seem to find the proper code to look at each file to count the words (I'm trying to find something "generic" rather than a specific, but I trying to test the program using a specific text file). This is the intended output:

Count 11 files:
word length: 1 ==> 80
word length: 2 ==> 321
word length: 3 ==> 643

However, this is what's being outputted instead:

primes.txt
but
are
sometimes
sense
refrigerator
make
haiku
dont
they
funny
word length: 1 ==> {but=1, are=1, sometimes=1, sense=1, refrigerator=1, make=1, haiku=1, dont=1, they=1, funny=1}

.....

Count 11 files:

I'm using two classes: WordCount and FileCatch8

WordCount:

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.AbstractMap.SimpleEntry;
import java.util.Arrays;
import java.util.Map;
import static java.util.stream.Collectors.counting;
import static java.util.stream.Collectors.groupingBy;

    /**
     *
     * @author 
     */
    public class WordCount {

        /**
         *
         * @param filename
         * @return
         * @throws java.io.IOException
         */
        public Map<String, Long> count(String filename) throws IOException {
            //Stream<String> lines = Files.lines(Paths.get(filename));
            Path path = Paths.get("haiku.txt");
            Map<String, Long> wordMap = Files.lines(path)
                    .parallel()
                    .flatMap(line -> Arrays.stream(line.trim().split(" ")))
                    .map(word -> word.replaceAll("[^a-zA-Z]", "").toLowerCase().trim())
                    .filter(word -> word.length() > 0)
                    .map(word -> new SimpleEntry<>(word, 1))
                    //.collect(Collectors.toMap(s -> s, s -> 1, Integer::sum));
                    .collect(groupingBy(SimpleEntry::getKey, counting()));

            wordMap.forEach((k, v) -> System.out.println(String.format(k,v)));
            return wordMap;
        }
    }

And FileCatch:

import java.io.IOException;
import java.nio.file.DirectoryStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author 
 */
public class FileCatch8 {
    public static void main(String args[]) {
        List<String> fileNames = new ArrayList<>();
        try {
            DirectoryStream<Path> directoryStream = Files.newDirectoryStream
        (Paths.get("files"));
            int fileCounter = 0;
            WordCount wordCnt = new WordCount();
            for (Path path : directoryStream) {
                System.out.println(path.getFileName());
                fileCounter++;
                fileNames.add(path.getFileName().toString()); 
                System.out.println("word length: " +  fileCounter + " ==> " + 
                        wordCnt.count(path.getFileName().toString()));
}
        } catch(IOException ex){
    }
    System.out.println("Count: "+fileNames.size()+ " files");

  }
}

The program uses Java 8 streams with lambda syntax

回答1:

Word count example:

Files.lines(Paths.get(file))
    .flatMap(line -> Arrays.stream(line.trim().split(" ")))
    .map(word -> word.replaceAll("[^a-zA-Z]", "").toLowerCase().trim())
    .filter(word -> !word.isEmpty())
    .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

Files count:

Files.walk(Paths.get(file), Integer.MAX_VALUE).count();
Files.walk(Paths.get(file)).count();

回答2:

In my opinion, the simplest way to count the words in a file using Java 8 is this:

Long wordsCount = Files.lines(Paths.get(file))
    .flatMap(str->Stream.of(str.split("[ ,.!?\r\n]")))
    .filter(s->s.length()>0).count();
System.out.println(wordsCount);

And to count all the files:

Long filesCount = Files.walk(Paths.get(file)).count();
System.out.println(filesCount);

来源：https://stackoverflow.com/questions/47594679/how-to-count-words-in-a-text-file-java-8-style