JAVA：用于文档比较的最佳数据结构？

Question

I am writing a program that compares multiple documents based on the words they have in common. I am able to tokenize all of the words and store all of them in an ArrayList since it allows duplicates. However, I am not sure that that is the best way of doing it. I need to find the top 50 most frequent words in the ArrayList, and I am not really sure how to do that. Is there a better data structure for this operation?

Answer 1

If you just want to compare occurrences, you can use a map such as a HashMap , TreeMap , or any other implementation .

The key will be the word (String), the value will be the number of occurrences (Integer). You'll go over your document, and lookup each word in the map. If it exists, get its current number of occurrences, and increment it by one. If it doesn't, insert the word with an occurrence count of zero. Here's a code snippet:

    HashMap<String, Integer> occurenceMap = new HashMap<>();

    for (String word : document) {
        Integer wordOccurences = occurenceMap.get(word);
        if (wordOccurences == null) {
            wordOccurences = Integer.valueOf(1);
        } else {
            wordOccurences += 1;
        }
        occurenceMap.put(word, wordOccurences);
    }