Что не так? Не понимаю...
package com.javarush.task.task18.task1825;
import java.io.*;
import java.util.SortedSet;
import java.util.TreeSet;
/*
Собираем файл
*/
public class Solution {
public static void main(String[] args) throws IOException {
SortedSet<String> treeSet = new TreeSet<>();
String fileName = null;
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
while (!bufferedReader.readLine().equals("end")) {
treeSet.add(fileName = bufferedReader.readLine());
}
bufferedReader.close();
// assert fileName != null;
int index = fileName.lastIndexOf('.');
String fileNameOutput = fileName.substring(0, index);
BufferedOutputStream outputStream = new BufferedOutputStream(new FileOutputStream(fileNameOutput, true));
for (String NameFile : treeSet) {
BufferedInputStream inputStream = new BufferedInputStream(new FileInputStream(NameFile));
while (inputStream.available() > 0)
outputStream.write(inputStream.read());
inputStream.close();
}
outputStream.close();
}
}