基于驼峰大小写的第n个单词对java字符串进行分组

import java.util.*;
import java.util.regex.*;

public class CamelCaseGrouping {
    public static void main(String[] args) {
        String input = "camelCaseStringExample";
        int n = 2; // 提取第2个单词

        Map<String, List<String>> grouped = groupByNthCamelCaseWord(input, n);
        System.out.println(grouped);
    }

    public static Map<String, List<String>> groupByNthCamelCaseWord(String input, int n) {
        Map<String, List<String>> grouped = new HashMap<>();
        Pattern pattern = Pattern.compile("(?<!(^|[A-Z]))(?=[A-Z])|(?<!^)(?=[A-Z][a-z])");
        Matcher matcher = pattern.matcher(input);

        List<String> words = new ArrayList<>();
        while (matcher.find()) {
            words.add(matcher.group());
        }

        if (words.size() < n) {
            throw new IllegalArgumentException("Input string does not contain enough words");
        }

        String nthWord = words.get(n - 1).toLowerCase();

        grouped.putIfAbsent(nthWord, new ArrayList<>());
        grouped.get(nthWord).add(input);

        return grouped;
    }
}