Stream API collect() 使用 personal class Word 而不是 Map

Question

我如何将我的地图转换为 class 包含单词及其频率的单词

List<Word>

或者我必须创建类似的东西

Map<String, List<Word>> wordFreq

我为了简洁避免了一些方法

public class Word implements Comparable<Word> {

    private String content;

    private int frequency;
}

class CONTAINER {
 public static void main(String[] args) {
 StringBuilder userWords = new StringBuilder();
userWords.append("some sequence of words");

Map<String, Long> wordFreq = Stream.of(userWords.toString().split(" ")).parallel()
                    .collect(Collectors.groupingBy(String::toString, Collectors.counting()));

            List<Word> words = new ArrayList<>();
            for (Map.Entry<String, Long> a : wordFreq.entrySet()) {
                words.add(new Word(a.getKey(), Math.toIntExact(a.getValue())));
            }
    words.forEach(s -> System.out.println(s.getContent() + " : " + s.getFrequency()));
  }
}

Answer 1

您可以使用Stream.map(..)方法。在你的情况下是：

List<Word> words = wordFreq.entrySet()
         .stream()
         .map(entry -> new Word(a.getKey(), Math.toIntExact(a.getValue())))
         .collect(Collectors.toList());

Answer 2

Map 中有一个 forEach 的便捷方法：

List<Word> words = new ArrayList<>();
Stream.of(userWords.toString().split(" "))
    .parallel()
    .collect(Collectors.groupingBy(String::toString, Collectors.counting()))
    .forEach((k, v) -> words.add(new Word(k, Math.toIntExact(v))))

Stream API collect() 使用 personal class Word 而不是 Map

Stream API collect() use personal class Word intsead of Map

java

collections

java-8

java-stream