Very confused as what is wrong

Question about the task

Resolved

The validation is a bit off. As it claims I do not close the stream. But maybe I am not allowed to use a TreeMap for this task?

Let's build a file from various pieces.
Read file names from the console.
Each file has a name: <someName>.partN.

For example, Lion.avi.part1, Lion.avi.part2, ..., Lion.avi.part37.

The file names are supplied in random order. The word "end" is used to stop reading in file names.
In the folder where all the files are located, create a file without the "part" suffix, i.e. without ".<partN>".

For example, Lion.avi.

Use a buffer to copy all the bytes from the partial files to the created file.
Copy the first in the proper order, first the first part, then the second, ..., finally - the last part.
Close the streams.

Requirements:

The program must read file names from the console until the word "end" is entered.
Create a stream to write to the file without the "part" suffix (".<partN>") in the folder with all the "part" files.
Copy all the bytes from the *.partN files to the new file.
You should use a buffer for the reading and writing.
The file streams must be closed.
Don't use static variables.

package com.codegym.task.task18.task1825; import java.io.*; import java.util.Map; import java.util.TreeMap; /* Building a file */ public class Solution { public static void main(String[] args) throws IOException { //Create a reader to read filenames from keyboard BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); //create a map for all filenames <String = .<partN>, String = fullFilename> Map<String, String> folder = new TreeMap<>();// place all entries in order //read filenames until "end" is entered String s; while (!(s = reader.readLine()).equals("end")) { s = reader.readLine();//reads the filenames //split the filenames .part<n> will be the key to be able to sort the files in the right order String partNumber = s.substring(s.lastIndexOf(".part")); folder.put(partNumber, s); } reader.close(); //create a file to which all content will be written to String file = folder.get(0);//returns the value of the first file which is a fileName including the partNumber String fileComposite = file.substring(0, file.lastIndexOf(".part"));//creates a fileName without the <.partN> //folder.put(fileComposite, fileComposite); //not sure if I have to add this file to the folder/map //create outputStream FileOutputStream fos = new FileOutputStream(fileComposite, true); //iterate over the map with filenames for (String fileName : folder.values()) { //create inputStream for each fileName FileInputStream fis = new FileInputStream(fileName); //create a buffer for all bytes read available() gives number of bytes to read byte[] buffer = new byte[fis.available()]; //read the bytes from a file and add it to the buffer while (fis.available() > 0) { int byteRead = fis.read(buffer); //write the buffer to outputStream file fos.write(buffer, 0, byteRead); } fis.close(); } fos.close(); } }

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Liliane Top Backend Developer at Procura

8 January 2021, 09:00

solution

Solved it after a good night sleep! So many mistakes 1) Changed the Map to TreeMap<Integer, String> folder 2) This mistake I keep making: on line 25 I repeat the reader.readLine() overwriting the one in line 24 so I remove it. 3) the substring of each fileName should only be the number without the word ".part" hence it should be lastIndexOf(".part") + 5)) and then parse that number into an Integer and add it to the TreeMap 4) To get a filename from the folder without knowing the key you can use folder.getFirstEntry().getValue(); This only works with a TreeMap and not just Map => so the signature should be changed from Map<Integer, String> into TreeMap<Integer, string> folder = new TreeMap<>(); 5) You do not have to add this output file to the folder to pass the test 6) Make sure you set value 'append' to true in the output file => FileOutputStream(outputFile, true);