如何去除句子中的停用词？

Question

I have a list of stopwords where I want to remove all stopwords that exist in a sentence from the stopword-list. I'm currently using regex. I have to convert it to lower case as per the requirements that i need to meet.

However, the problem is that stopwords still exists in the sentence.

// List of stopwords
List<String> stopwords = new ArrayList<>();
stopwords.add("is");
stopwords.add("a");
// the stopword list goes on ....

// Sentence
String sentence = "autism    autism is a neurodevelopmental";

// Remove stop words in the sentence
String stopwordsRegex = stopwords.stream().collect(Collectors.joining("|", "\\b(", ")\\b\\s?"));
String removedSW = sentence.toLowerCase().replaceAll(stopwordsRegex, "");

System.out.println(removedSW);

Answer 1

String stopwordsRegex = stopwords.stream()
        .map(String::toLowerCase)
        .collect(Collectors.joining("|", "(?i)\\b(", ")\\b\\s?"));
String removedSW = sentence.replaceAll(stopwordsRegex, "");

Everything is fine, just (?i) will add an ignore-case , so the sentence may keep its upper case. It might have been an upper-case stop word like "I" . How to make words in a stream lower-case added (but not necessary).

Answer 2

this works as well:

 for (String stopword : stopwords){
      sentence = sentence.replaceAll("\\b" + stopword + "\\b", "");
 }