MatchingWords (task 55)

What's wrong in this code? (for Matching Words problem)

import java.util.Scanner;
import java.util.ArrayList;
import java.util.Arrays;

public class MatchingWords{

    public static void main(String[] args){
        Scanner scr = new Scanner(System.in);
        String data = scr.nextLine();
        String answer = matchingWords(data);
        System.out.println(answer);
    }

    public static String matchingWords(String str){
        String result = new String();

        String[] tmp = str.split(" ");
        ArrayList<String> list = new ArrayList(Arrays.asList(tmp));

        while (true){
            String compar = list.get(0);
            if (compar.equals("end"))
                break;

            list.remove(0);

            if (list.contains(compar)){
                result += compar + " ";
                list.remove(compar);
            }
        }

        return result;
    }
}

when I give as input example in problem answer matches.

P.S. Sorry for my bad English.

Thank for your help, smwentum! I do this.