문자열 곱하기

https://school.programmers.co.kr/learn/courses/30/lessons/181940

• 문제 풀이

public class Solution {
    public String solution(String my_string, int k) {
        StringBuilder result = new StringBuilder();
        for (int i = 0; i < k; i++) {
            result.append(my_string);
        }
        return result.toString();
    }
}