두 개 뽑아서 더하기

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

class Solution {
    public int[] solution(int[] numbers) {

        ArrayList<Integer> list = new ArrayList<Integer>();

        for(int i = 0; i < numbers.length ; i++){
            for(int j = i+1; j < numbers.length ;  j++){

                int a = numbers[i] + numbers[j];
                    if(list.indexOf(a) < 0){   
                        list.add(a);
                    }
            }

        }



        int[] answer = new int[list.size()];

        for(int i = 0; i < list.size(); i++){
            answer[i] = list.get(i);
        }
        Arrays.sort(answer);

        return answer;

    }


}