java - 词频计数器，列表无法正常工作

Question

我有一些代码可以计算给定单词 ArrayList 中的单词频率。我有一个频率类，它主要存储单词及其各自的频率。这是我的代码:

public static List<Frequency> computeWordFrequencies(List<String> words) {
        List<String> wordsList = words; 
        String[] wordsArray = wordsList.toArray(new String[0]);
        Arrays.sort(wordsArray);
        Set<String> noDuplicates = new LinkedHashSet<>(Arrays.asList(wordsArray));
        List<Frequency> frequencies = new ArrayList<>();
        for (String word : noDuplicates) {
            int wordFrequency = Collections.frequency(words, word);
            Frequency newFrequency = new Frequency(word, wordFrequency);
            System.out.println(newFrequency.toString());
            frequencies.add(newFrequency);
        }
        for (Frequency f : frequencies) {
            System.out.println(f.getText()+"               "+f.getFrequency());
        }
        return frequencies; 
    }

供引用，频率等级:

public class Frequency {

    private final String word;
    private static int frequency;

    public Frequency(String word) {
        this.word = word;
        frequency = 0;
    }

    public Frequency(String word, int newfrequency) {
        this.word = word;
        this.frequency = newfrequency;
    }

    public String getText() {
        return word;
    }

    public int getFrequency() {
        return frequency;
    }

    public static void setFrequency(int newFrequency) {
        frequency = newFrequency;
    }

    public void incrementFrequency() {
        frequency++;
    }

    @Override
    public String toString() {
        return word + ":" + frequency;
    }

}

我在我的代码中插入了 print 语句，这是一些输出:

wrapping:1 yard:3 yarn:2 year:2 yet:1 yukon:1 zero:2 abandoned
2 accordion 2 acequia 2 across
2 added 2

所以当创建频率时，它们具有正确的频率，但不知何故它们后来都变成了 2。更奇怪的是，如果我将第二个打印语句更改为 f.toString()，即使是第一个打印语句只显示 2 个这样的频率:

rising:2 river:2 riveredge:2 riversound:2 road:2 roadrunners:2 roadside:2 roast:2

谁能告诉我为什么所有频率都设置为 2，或者问题出在哪里？

Answer 1

删除 static来自

private static int frequency

您希望每个单词都有一个单独的实例变量，而不是所有单词都有一个类变量。

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另外，我会推荐 Hashmap<String, Integer>对于频率计数器而不是创建任何包装对象，因为......

1. 没有理由将列表转换为数组，然后转换为集合，然后再转换回列表
2. 在删除重复项之前不需要对列表进行排序
3. Collections.frequency一个循环内的运行时间为 O(n^2)