프로그래머스 전화번호 목록 (자바)

import java.util.Arrays;
class Solution {
    public static boolean solution(String[] phone_book) {
        boolean answer = true;
        Arrays.sort(phone_book);
        for (int i = 0; i < phone_book.length-1; i++) {
            String longStr;
            String shortStr;
            if(phone_book[i].length()>phone_book[i+1].length()){
                longStr = phone_book[i];
                shortStr = phone_book[i+1];
            }
            else{
                shortStr = phone_book[i];
                longStr = phone_book[i+1];
            }
            if(shortStr.equals(longStr.substring(0,shortStr.length()))){
                answer=false;
                break;
            }
        }
        return answer;
    }
}