And another one where is the mistake?

Question about the task

Combining files

Java Core, Level 8, Lesson 11

Under discussion

Please help frustration is getting a but much with the useless feedback of my mentor ;-).

Read 2 file names from the console.
Write the contents of the second file to the beginning of the first file so that the files are combined.
Close the streams.

Requirements:

The program should read a file name twice from the console.
Create an input stream for the first file and read its contents.
Then create an output stream for the first file. And an input stream for the second file.
The contents of the first and second files must be combined in the first file.
The contents of the second file should go first, then the contents of the first file.
The file streams must be closed.

package com.codegym.task.task18.task1819; /* Combining files TODO: Write the contents of the second file to the beginning of the first file so that the files are combined. */ import java.io.*; public class Solution { public static void main(String[] args) throws IOException { //TODO: read 2 files from the console BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String file1 = reader.readLine(); String file2 = reader.readLine(); reader.close(); //TODO: Create an input stream for the first file and read its contents. FileInputStream inputStreamFile1 = new FileInputStream(file1); FileOutputStream outputStreamFile2 = new FileOutputStream(file2, true); while (inputStreamFile1.available() > 0) { int a = inputStreamFile1.read(); outputStreamFile2.write(a);//write the contents of file1 naar file2 append (at the end) } inputStreamFile1.close(); outputStreamFile2.close(); //TODO: Then create an output stream for the first file. // And an input stream for the second file. FileOutputStream outputStreamFile1 = new FileOutputStream(file1); FileInputStream inputStreamFile2 = new FileInputStream(file2); //TODO: read file 2 (all of its contents of file1 and file2 and copy it to file 1 overwriting the existing text while (inputStreamFile2.available() > 0) { int b = inputStreamFile2.read(); outputStreamFile1.write(b);//overwriting the existing text } outputStreamFile1.close(); inputStreamFile2.close(); } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

3 January 2021, 16:38

While your end result matches the expected results, the steps that you take are not the steps that are specified in this task. I would recommend doing exactly what the task says to do: The validation system does not have files on a virtual computer that you have unlimited access to, it has hard coded values that it will replace your streams with and pump in the data. This means that you are not able to change those values. So when you write file1 to file2, it doesn't actually do that as it would with folders on your system. When you do this the validation system isn't able to determine what is the error, and as your frustration can attest to, isn't able to explain exactly what is wrong. So do this: read both the data from file 1 and from file 2, saving them in proper containers, then write those to file1 in the correct order

Liliane Top Backend Developer at Procura

3 January 2021, 17:27

Yep, I have access to the solutions. But was wondering if there was something wrong with my code. Probably not. I'm also playing with JDK 11 but Codegym can't compile it which is rather odd.

Guadalupe Gagnon

Level 37 , Tampa, United States

4 January 2021, 00:03

The problem with your solution was how you wrote to file 2 and then to file 1. The validator does not have a hard drive where these files are saved such as your computer has, they are not files but hard coded values only used in the validator. This means that you can't read/write to them unless specifically told to do in the task directions. No where in this task does it say to write to file 2. Because your code does this, and the validator can't handle it, it bugs out.

Nouser

Level 36 , Germany

4 January 2021, 09:37

I remember that I had a hard fight with the validator, too. And as you here suggested, I followed the requirements to the word after some tries. That worked. But I continued trying and also verified the approach Liliane now tried, too. Unfortunately I didn't keep the entire code but just the main part of it.

FileInputStream in1 = new FileInputStream(file1);
FileInputStream in2 = new FileInputStream(file2);
FileOutputStream outWithAppendEnabled = new FileOutputStream(file2, true);

while (in1.available() > 0)
    outWithAppendEnabled.write(in1.read());

FileOutputStream outWithoutAppend = new FileOutputStream(file1, false);

while (in2.available() > 0)
    outWithoutAppend.write(in2.read());

If I had to guess what's up with the validator, I'd start with removing the reader objects close call (cause of point 2 and 3, maybe the vlidator just looks for the wording close at the end of the code and that is to early for it).