백준 1764번 (듣보잡) 2회차

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import java.util.*;

import static java.util.Collections.*;

public class Main {
public static void main(String[] args) throws IOException {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

    StringTokenizer st = new StringTokenizer(br.readLine());

    int N = Integer.parseInt(st.nextToken());
    int M = Integer.parseInt(st.nextToken());

    HashSet<String> hash = new HashSet<>();
    List<String> list = new ArrayList<>();




    for (int i = 0 ; i < N; i++)
    {
        hash.add(br.readLine());
    }

    for (int j = 0 ; j < M; j++)
    {
        String word = br.readLine();


        if (hash.contains(word) )
        {
           list.add(word);
        }

    }

    Collections.sort(list);

    System.out.println(list.size());
    for (String s : list) {
        System.out.println(s);
    }





}
}

이전에 풀어서 그런지 잘풀렸다.