Level 30

Chennai

14.08.2020
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10comments

help

Question about the task

Resolved

can't verify the 3rd and 4th requirement

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; import java.io.*; import java.util.*; /* Combining files */ public class Solution { public static void main(String[] args) throws Exception{ BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); File f1 = new File(br.readLine()); File f2 = new File(br.readLine()); FileInputStream fis1 = new FileInputStream(f1); byte[] b1 = new byte[fis1.available()]; int count = fis1.read(); FileOutputStream fos = new FileOutputStream(f1); FileInputStream fis2 = new FileInputStream(f2); byte[] b = new byte[fis2.available()]; int count1 = fis2.read(); fos.write(count1); fos.write(b1); fis1.close(); fis2.close(); fos.close(); } }

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Nouser

Level 36 , Germany

14 August 2020, 10:10

fis1.read() just reads one byte... and that one not into the byte array Same for fis2.read(); Now you have two arrays with nothing in it and two ints (count1 and count) with each containing one byte and finally you write one empty array and one int?

dhanush

Level 30 , Chennai, India

14 August 2020, 13:12

Thanks for replaying. But the line 17 reads the whole file how it can be an empty array

byte[] b1 = new byte[fis1.available()];

then actually i used boolean append to copy the file to the end of first file but it ends with an error,

fos.write(b,true);

Nouser

Level 36 , Germany

14 August 2020, 15:45

solution

this just creates an array with a specific size, the file size in bytes, it doesn't read the file. You can easily test it with outputting the array on screen. Your solution should look similar to:

byte[] b1 = new byte[fis1.available()];
fis1.read(b1);

dhanush

Level 30 , Chennai, India

15 August 2020, 05:27

Oh i actually thought that line itself read the whole file, Thank you but how can i write the first file in the end of the file i tired using the boolean append itself it's not working can you tell which method it used to append to the end of the file

Nouser

Level 36 , Germany

15 August 2020, 06:20

useful

You do that whilst initializing the FileOutputStream within the constructor

FileOutputStream(String name, boolean append)

But you shouldn't need that if you just open one output stream and write both arrays using that stream, the second file of course first.

dhanush

Level 30 , Chennai, India

15 August 2020, 06:34

Yeah actually now i understand clearly the task asks for read and write the full mean the whole file but the second file first and the first file while i'm doing with

byte[] b = new byte[fis.available()];

it doesn't read the whole as you said it just read an one array or an empty array. I have completed the task using the while loop,

while(fis.available()>0){
int count = fis.read();
fos.write(count);
}

Thanks for helping me with the task. :)

dhanush

Level 30 , Chennai, India

15 August 2020, 06:36

Initialize the FileOutputStream within the constructor means, can you give me an example of that.

Nouser

Level 36 , Germany

15 August 2020, 06:40

sure...

FileOutputStream fos = new FileOutputStream(f1, true);

And you can code the instructions nearly word for word. Have a look at my solution.

//1. The program should read a file name twice from the console.
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String fileName1 = reader.readLine();
        String fileName2 = reader.readLine();
        reader.close();

        //2. Create an input stream for the first file and read its contents.
        BufferedInputStream source1 = new BufferedInputStream(new FileInputStream(fileName1));
        byte[] file1Buffer = new byte[source1.available()];
        source1.read(file1Buffer);

        //3. Then create an output stream for the first file. And an input stream for the second file.
        BufferedOutputStream target = new BufferedOutputStream(new FileOutputStream(fileName1));
        BufferedInputStream source2 = new BufferedInputStream(new FileInputStream(fileName2));

        //4. The contents of the first and second files must be combined in the first file.
        //for that we need to read the contents of file2 first
        byte[] file2Buffer = new byte[source2.available()];
        source2.read(file2Buffer);

        //5. The contents of the second file should go first, then the contents of the first file.
        target.write(file2Buffer);
        target.write(file1Buffer);

        //6. The file streams must be closed.
        target.close();
        source1.close();
        source2.close();

dhanush

Level 30 , Chennai, India

15 August 2020, 06:52

Much more clearer now. Thanks mate for helping. :)

Nouser

Level 36 , Germany

15 August 2020, 07:07

You're welcome :)