문자열 겹쳐쓰기

class Solution {
    public String solution(String my_string, String overwrite_string, int s) {
        String answer = "";
        
        answer = my_string.substring(0,s) + overwrite_string + my_string.substring(s+overwrite_string.length());
        
        
        return answer;
        //substring (start포함,end제외);
        
    }
}

• substring(start 포함, end 제외)