Not good obviously, but what do you guys think about my solution

Question about the task

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I sick and tired from this one, I know that it is no good, but wanted to know what do you guys think about it, and what is wrong, I cant look at it anymore, and I have to move on to the next one, because i am stuck at this problem for far too long..

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.BufferedReader; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStreamReader; import java.util.*; /* Building a file */ public class Solution { public static void main(String[] args) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String fileName; String outputFile = ""; Map<String, Integer> map = new TreeMap<>(); while(!(fileName = reader.readLine()).equals("end")){ String[]split = fileName.split("."); if(split.length>2){ int partNum = Integer.parseInt(split[2].substring(4)); map.put(fileName, partNum); } else{ outputFile = fileName; } } for(Map.Entry<String, Integer> entry : map.entrySet()){ String key = entry.getKey(); FileInputStream fis = new FileInputStream(key); byte[]buffer = new byte[fis.available()]; fis.read(buffer); FileOutputStream fos = new FileOutputStream(outputFile); fos.write(buffer); fis.close(); fos.close(); } } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

12 November 2019, 14:58

#1 TreeMap is used in the wrong way. The order is going to be incorrect without providing a custom comparator. It would be better to make the map Integer, String instead of String, Integer. #2 Line 24 will always be true and line 29 will never be reached, this means outputFile is never set. #3 The code overwrites the output every time a new output stream (line 38) is created. This means the output file will only have the data from the very last file. You may be able to set append to true and complete the task, but I would write everything after you have saved all the input data. Some tips: Use this structure for all input/output streams:

try(BufferedReader reader = new BufferedReader(new InputStreamReader(System.in))){
    // code that uses stream
}

1) This is a cleaner way of using streams and they automatically close after usage. You can even use catch blocks with this if it is called for. 2) I would split the filenames like this: fileName.split(".part") - now the full filename is at index 0 and the number is at index 1. 3) Use this inside the loop at line 22: if (outputFile.isEmpty()) - if this returns true you can set filename properly. 4) When you are reading bytes like you do in this code in the loop at line 33, you can save all that data in a ByteArrayOutputStream object. It is easy to use. Declare it outside the loop, the constructor doesn't take any arguments that you need. Then, when you read data, you can store that data inside of the BAOS like this:

byte[] buffer = new byte[fis.available()];
fis.read(buffer);
baos.write(buffer);

Once you are done reading in data you can use access all the stored data and write it like this:

try(FileOutputStream fis = new FileOutputStream(outputFile)){
   fis.write(baos.toByteArray());
}

Good Luck!

Picvajzmen

Level 20 , Belgrade, Serbia

14 November 2019, 06:43

I do not know should i hate you or love you for this answer... :) Plenty to learn and study now, ill let you know when i am done. Thank you.

Guadalupe Gagnon

Level 37 , Tampa, United States

14 November 2019, 14:42

I hope you don't hate me =P. I do enjoy breaking down other people's code and understanding it. I personally learn a lot by doing this. Here is a little bit more info specifically from the points i made above: #1 I should have specifically said above that TreeMap is a great way to solve this and when you switch it to Integer,String it will automatically sort the keys in ascending order without you having to do a comparator. #3 Just move line 38 to line 32; and line 41 to line 43 in the tips: #2 fileName.split(".part") When you use this for a string like "Lion.avi.part37" the array would be ["Lion.avi", "37"]. You can use the first part to set outputFile and the second part as the key inside the Treemap(Integer, String). I hope these further explanations/tips are helpful.

Picvajzmen

Level 20 , Belgrade, Serbia

15 November 2019, 10:00

They are very helpful, and i seriously think that CodeGym should pay you for your work, i know you are learning that way also, and that is the point, but if there is no question/help area, the whole course would be completely different and a lot harder. And the question/help area is non existent without you and others who try and help, but mostly you. TreeMap uses key to sort its content, not values, i read that yesterday.. It makes sense.

Picvajzmen

Level 20 , Belgrade, Serbia

15 November 2019, 10:34

Solved in 27 attempts. Not my personal record though. I made a mistake(one of many) that i was trying to find the one file that is without the <part> suffix, and that was unnecessary actually.