Can someone explain to me where i made a mistake ?

package pl.codegym.task.task18.task1825; import java.io.*; import java.util.*; /* Tworzenie pliku */ public class Solution { public static void main(String[] args) throws IOException { TreeMap<Integer, File> treeMap = new TreeMap<>(); String[ ] tab; BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String file1 = reader.readLine(); tab = file1.split("\\.part"); treeMap.put(Integer.parseInt(tab[1]),new File(file1)); FileOutputStream fileOutputStream = new FileOutputStream(tab[0],true); while(true) { file1 = reader.readLine(); if(file1.equals("end")){ break;} else{ tab = file1.split("\\.part"); treeMap.put(Integer.parseInt(tab[1]),new File(file1)); } } reader.close(); for (Map.Entry<Integer, File> para : treeMap.entrySet()) { FileInputStream fileInputStream = new FileInputStream(para.getValue()); byte[] bytes = new byte[fileInputStream.available()]; while (fileInputStream.available() > 0) { int count = fileInputStream.read(bytes); fileOutputStream.write(bytes,0,count); } fileInputStream.close(); } fileOutputStream.close(); } }