Данные в файл вроде верно пишет.
package com.javarush.task.task18.task1825;
import java.io.*;import java.util.*;
public class Solution {
public static void main(String[] args) throws IOException {
ArrayList<String> arList = new ArrayList<>();
ArrayList<String> list = new ArrayList<>();
TreeMap<Integer, String> map = new TreeMap<>();
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String namefile = reader.readLine();
try {
while (!namefile.equals("end")) {
arList.add(namefile);
namefile = reader.readLine();
}
reader.close();
FileOutputStream fos = new FileOutputStream("D:/JavaRushTasks/Lion.avi.txt");
int i;
for (String str : arList) {
FileReader fileReader = new FileReader(str);
BufferedReader br = new BufferedReader(fileReader);
int num = 0;
String line;
while((line = br.readLine()) != null) {
str = str.replaceAll("[^\\d]", "");
num = Integer.parseInt(str);
map.put(num, line);
}
fileReader.close();
br.close();
}
for(Map.Entry <Integer, String> entry: map.entrySet()) {
String value = entry.getValue();
list.add(value);
}
StringBuilder buffer = new StringBuilder();
for (String a : list) {
buffer.append(a);
}
byte[] bytes = buffer.toString().getBytes();
for (byte a : bytes) {
fos.write(a);
}
fos.close();
FileInputStream fis = new FileInputStream("D:/JavaRushTasks/Lion.avi.txt");
while((i = fis.read())!= -1) {
System.out.print((char) i);
}
fis.close();
} catch (FileNotFoundException e) {}
}
}