проверяю, в файлике все строки на месте.
package com.javarush.task.task13.task1319;
import java.io.*;
public class Solution {
public static void main(String[] args) throws IOException {
// напишите тут ваш код
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String line =reader.readLine();
BufferedWriter writer = new BufferedWriter(new FileWriter(line));
writer.write(line+ "\n");
while (true) {
line = reader.readLine();
if (line.equals("exit")) {
writer.write(line);
break;
} else writer.write(line + "\n");
}
writer.close();
}
}