프로그래머스 Lv1 3진법 뒤집기

import java.util.*;

class Solution {

    public static void main(String[] args) {
        Solution s = new Solution();
        tester(45,7,s);
        tester(125,229,s);

    }

    public static void tester(int n, int result,Solution s)  {

        int ret = s.solution(n);

        if(ret == result) {
            System.out.println("OK");
        }
        else {
            System.out.println("NG");
        }
    }


    public int solution(int n) {
        int answer = 0;

        StringBuilder sb = new StringBuilder();

        int r=0;
        while (n!=0) {
            r = n%3;
            n = n/3;
            sb.append(r);
        }
        sb.reverse();
        //char[] jinsu3 = sb.toString().toCharArray();
        String jinsu3 = sb.toString();


        for(int i=0 ; i<jinsu3.length() ; i++) {
            String sbstr = jinsu3.substring(i,i+1);

            answer += (int)Math.pow(3,i) * Integer.parseInt(sbstr);
        }

        return answer;
    }
}