按频率对文本文件中的单词进行排序

Question

I've created a program which calculates the amount of distinct words in a text document, and then prints them out to the console. What I want to add to the program is that the words should be sorted by the highest frequency. I'm sure this is nothing major to add, but I'm clueless on what to do.

This is the code:

public static void main(String[] args) throws FileNotFoundException, IOException {

Map<String, Integer> fileReaderMap = new HashMap<>();

try (BufferedReader br = new BufferedReader(new FileReader("file.txt"))) {
    StringBuilder sb = new StringBuilder();
    String line = br.readLine();

    while (line != null) {
    String[] words = line.split(" ");
    for (int i = 0; i < words.length; i++) {
        if (!fileReaderMap.containsKey(words[i])) {
        fileReaderMap.put(words[i], 1);
        } else {
        int newValue = fileReaderMap.get(words[i]) + 1;
        fileReaderMap.put(words[i], newValue);
        }
    }
    sb.append(System.lineSeparator());
    line = br.readLine();
    }
}

Answer 1

First use a Map to count the appearances of the words. And then put the entries of your Map in a List and sort it using Collections.sort() and a comparator. Than you can just print the sorted List:

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

public class Snippet {

    public static void main(String[] args) throws FileNotFoundException, IOException {

    Map<String, Integer> fileReaderMap = new HashMap<>();

    try (BufferedReader br = new BufferedReader(new FileReader("file.txt"))) {
        StringBuilder sb = new StringBuilder();
        String line = br.readLine();

        while (line != null) {
        String[] words = line.split(" ");
        for (int i = 0; i < words.length; i++) {
            if (!fileReaderMap.containsKey(words[i])) {
            fileReaderMap.put(words[i], 1);
            } else {
            int newValue = fileReaderMap.get(words[i]) + 1;
            fileReaderMap.put(words[i], newValue);
            }
        }
        sb.append(System.lineSeparator());
        line = br.readLine();
        }
    }
    List<Entry<String, Integer>> sorted = new ArrayList<>(fileReaderMap.entrySet());
    Collections.sort(sorted, new Comparator<Entry<String, Integer>>() {
        @Override
        public int compare(Entry<String, Integer> o1, Entry<String, Integer> o2) {
        int comp = Integer.compare(o1.getValue(), o2.getValue());
        if (comp != 0) {
            return comp;
        }
        return o1.getKey().compareTo(o2.getKey());
        }
    });

    for (Entry<String, Integer> entry : sorted) {
        System.out.println("Ord: " + entry.getKey() + "\t Antal Gånger: " + entry.getValue());
    }
    }
}

Answer 2

TreeMap sorts on the basis of key. What you want to do is sort on the basis of value. You can create a class say Frequency, having fields as String word and int freq . Then you can iterate over hashmap and store these keys and values in their respective fields of this class. By traversing you can create a ArrayList of Frequency and using Comparable/Comparator you can sort on the basis of 'freq`.