java exercise to use regex in order to delete repeated words, case insensitive, in a sentence

findRepeatingWords.java

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import static java.util.regex.Pattern.CASE_INSENSITIVE;
import java.util.ArrayList;

public class DuplicateWords {

    public static void main(String[] args) {
        /*
          https://stackoverflow.com/a/37143875/3673430
        
          \\b([a-zA-Z]+)(\\b\\s\\1)+          takes also word parts
         (\\b[a-zA-Z]+\\b\\s?)(\\b\\1\\b)+    doesn't work with words at the end of line
         \\b([a-zA-Z]+)(\\b\\s\\b\\1\\b)+     works
         \\b([a-z]+)(\\s\\b\\1\\b)+    more efficient 
        */
        
        String regex = "\\b([a-z]+)(\\s\\b\\1\\b)+";
        Pattern p = Pattern.compile(regex, CASE_INSENSITIVE);

        Scanner in = new Scanner(System.in);
        int numSentences = Integer.parseInt(in.nextLine());
        
        while (numSentences-- > 0) {
            String input = in.nextLine();
            Matcher m = p.matcher(input);            
            
            while (m.find()) {
                   
                input = input.replaceAll(m.group(), m.group(1));
            }            
            
            System.out.println(input);
        }
        
        in.close();
    }
}