如何按频率对单词进行排序

Question

I take an input text file, convert it to an array, sort the array, and then get the frequencies of each word. I can't figure out how to sort them according to their frequencies, from highest to lowest, without importing lots of things (which is what I am trying to do):

//find frequencies
    int count = 0;
    List<String> list = new ArrayList<>();
    for(String s:words){
        if(!list.contains(s)){
            list.add(s);
        }
    }
    for(int i=0;i<list.size();i++){
        for(int j=0;j<words.length;j++){
            if(list.get(i).equals(words[j])){
                count++;
            }
        }

        System.out.println(list.get(i) + "\t" + count);
        count=0;
    }

This returns the words with their frequencies in an unsorted order, for example:

the 3
with 7
he 8

etc.

I want this to be sorted like:

he 8
with 7
the 3

Answer 1

I would suggest using a small helper class:

class WordFreq implements Comparable<WordFreq> {
   final String word;
   int freq;
   @Override public int compareTo(WordFreq that) {
     return Integer.compare(this.freq, that.freq);
   }
}

Build an array of instances of this class, one for each word, then sort the array using Arrays.sort .

Answer 2

I implemented it like so,

private static class Tuple implements Comparable<Tuple> {
    private int count;
    private String word;

    public Tuple(int count, String word) {
        this.count = count;
        this.word = word;
    }

    @Override
    public int compareTo(Tuple o) {
        return new Integer(this.count).compareTo(o.count);
    }
    public String toString() {
        return word + " " + count;
    }
}

public static void main(String[] args) {
    String[] words = { "the", "he", "he", "he", "he", "he", "he", "he",
            "he", "the", "the", "with", "with", "with", "with", "with",
            "with", "with" };
    // find frequencies
    Arrays.sort(words);
    Map<String, Integer> map = new HashMap<String, Integer>();
    for (String s : words) {
        if (map.containsKey(s)) {
            map.put(s, map.get(s) + 1);
        } else {
            map.put(s, 1);
        }
    }
    List<Tuple> al = new ArrayList<Tuple>();
    for (Map.Entry<String, Integer> entry : map.entrySet()) {
        al.add(new Tuple(entry.getValue(), entry.getKey()));
    }
    Collections.sort(al);
    System.out.println(al);
}

Output is,

[the 3, with 7, he 8]

Answer 3

You should create an object of type Word that holds the word's String value and its frequency.

Then you can implement compareTo or use a Comparator and call Collections.sort() on your list of type Word

Answer 4

使用Map<String, Integer>代替将String作为键存储，频率作为值存储，初始值为1.如果单词已经存在，只需将值增加1.然后将此映射转换为Map<Integer, List<String>> （或Guava Multimap ）并使用Integer值作为键，使用String键将它们存储为值。