글자 이어 붙여 문자열 만들기

class Solution {
    public String solution(String my_string, int[] index_list) {
        String answer = "";
        String[] my_stringIndex = my_string.split("");
        
        for(int i=0; i<index_list.length; i++){
           answer += my_stringIndex[index_list[i]];
        }
        
        return answer;
    }
}

 

 

class Solution {
    public String solution(String my_string, int[] index_list) {

        StringBuilder sb = new StringBuilder();

        for (int idx : index_list)
            sb.append(my_string.charAt(idx));

        return sb.toString();
    }
}