Поиск

package com.company;

import java.io.*;
import java.util.*;

public class Main {

    public static void main(String[] args) throws IOException {
        String encoding = "UTF-8";

        Scanner sc = new Scanner(System.in);
        System.out.println("Введите фамилии через пробел: ");
        String input = sc.nextLine();

        Set<String> lastNames = new HashSet<>(Arrays.asList(input.split(" ")));

        System.out.println("Найденные совпадения: ");
        try (BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream("src/com/company/input.txt"), encoding))) {
            for (String line; (line = reader.readLine()) != null; ) {
                int separator = line.indexOf(' ');
                String lastName = line.substring(0, separator);

                if (lastNames.contains(lastName)) {
                    System.out.println(line);
                }
            }
        }
    }
}