может чтото не так понимаю
package com.javarush.task.task18.task1825;
/*
Собираем файл
M:\JAVA\LION\lion.txt.part1
M:\JAVA\LION\lion.txt.part4
M:\JAVA\LION\lion.txt.part3
M:\JAVA\LION\lion.txt.part5
M:\JAVA\LION\lion.txt.part2
*/
import java.io.*;
import java.util.TreeSet;
public class Solution {
public static void main(String[] args) throws IOException {
String fileName;
TreeSet<String> parts = new TreeSet<>();
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
while (!(fileName = br.readLine()).equals("end")) {
parts.add(fileName);
}
for(String s: parts){
FileInputStream fis = new FileInputStream(s.substring(0,s.lastIndexOf('.')));
BufferedInputStream bis = new BufferedInputStream(fis);
FileOutputStream fos = new FileOutputStream("M:\\JAVA\\LION\\Lion.txt", true);
BufferedOutputStream bos = new BufferedOutputStream(fos);
bos.write(bis.read());
fis.close();
bis.close();
fos.close();
bos.close();
}
}
}