소팅 부분을 직접 구현하는 형식으로 코드를 짜봤는데요..

public class PracticeWedding {
    public int  solution(int number, List<List<String>> time){
        int answer = 0;//

        for (int i =0 ; i < number; i++){
            List<String> schdule = time.get(i);
            //시간 가져오기
            String strTime = schdule.get(0);
            //변환
            int intTime = Integer.parseInt(strTime);
            //state 가져오기
            String state = schdule.get(1);

            for (int j = i+1; j < number ; j++){
                List<String> schdule2 = time.get(j);
                //시간 가져오기
                String strTime2 = schdule2.get(0);
                //변환
                int intTime2 = Integer.parseInt(strTime2);
                //state 가져오기
                String state2 = schdule2.get(1);
                if (intTime > intTime2){
                    List<String>temp = new ArrayList<>();
                    temp = time.get(i);
                    time.set(i,time.get(j));
                    time.set(j,temp);

                }else if (intTime == intTime2){

                    if (state.equals("e")&&state2.equals("s")){
                        List<String>temp2 = new ArrayList<>();
                        temp2 = time.get(j);
                        time.set(j,time.get(i));
                        time.set(i,temp2);
                    }
                }
            }
            for (int z =1; z <time.size();z++){
                System.out.print(time.get(z));
            }
            System.out.println(" ");
        }

        //e와 s 판별
        for (int z=0; z<number; z++){
            List<String> schdule = time.get(z);
            String state = schdule.get(1);
            if (state.equals("s")){
                answer++;
            }else {
                answer--;
            }
        }
        return answer;

    }


    public static void main(String[] args) {

        PracticeWedding practice1 = new PracticeWedding();
        System.out.println("결혼식에 참석할 인원 수를 입력해주세요");
        Scanner intput = new Scanner(System.in);
        String peoplNumber = intput.next();
        List<List<String>>totalTimeArray = new ArrayList<>();
        int number = Integer.parseInt(peoplNumber);
        for (int i = 0; i < number; i++ ){

            System.out.println(i+"번째 돌아가는 친구의 시간을 입력하시오");
            Scanner scanner = new Scanner(System.in);
            String totalTime = scanner.nextLine();
            String[] array = totalTime.split(" ");
            String startTime = array[0];
            String endTime = array[1];
            List<String> manScheduleS = new ArrayList<>();
            manScheduleS.add(startTime);
            manScheduleS.add("s");
            totalTimeArray.add(manScheduleS);
            List<String> manScheduleE = new ArrayList<>();
            manScheduleE.add(endTime);
            manScheduleE.add("e");
            totalTimeArray.add(manScheduleE);
        }
        int Number = practice1.solution(number,totalTimeArray);
        System.out.println("Number = " + Number);
    }