Struggling with "off" and "len"

Question about the task

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The lessons are teaching me less and less. I've failed this task like half a dozen times already. So I check if my count is even or odd. If odd (count % 2 != 0), I write from 0 the first count / 2 characters. So, if I had 7 bytes, 7 / 2 should give me 3. 0-3. Then I write starting at count / 2 (or 3) to count/2 + 1, which should be 4 additional characters. 3 + 4 = 7, and the larger half is in the second file. What am I missing?

Read 3 file names from the console: file1, file2, file3.
Split file1 as follows:
Write the first half of its bytes to file2,and write the second half of its bytes to file3.
If the number of bytes in file1 is odd, then file2 should contain the larger half.
Close the streams.

Requirements:

The program should read a file name three times from the console.
Use FileInputStream to read from a file, and use FileOutputStream to write to files.
The first half of the bytes in the first file must be written to the second file.
The second half of the bytes in the first file must be written to the third file.
The FileInputStream and FileOutputStream must be closed.

package com.codegym.task.task18.task1808; /* Splitting a file */ import java.io.BufferedReader; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.InputStreamReader; public class Solution { public static void main(String[] args) throws Exception{ BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String file1 = reader.readLine(); String file2 = reader.readLine(); String file3 = reader.readLine(); reader.close(); FileInputStream inputStream = new FileInputStream(file1); FileOutputStream outputStream = new FileOutputStream(file2); FileOutputStream outputStream1 = new FileOutputStream(file3); byte[] buffer = new byte[inputStream.available()]; while (inputStream.available() > 0) { int count = inputStream.read(buffer); if (count % 2 != 0) { outputStream.write(buffer, 0, (count / 2)-1); outputStream1.write(buffer, (count / 2) -1, (count / 2) + 1); } else { outputStream.write(buffer, 0, count / 2); outputStream1.write(buffer, count / 2, count / 2); } } inputStream.close(); outputStream.close(); outputStream1.close(); } }

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Oliver Heintz

Level 18 , Mustang, United States

8 March 2021, 04:42

Holy balls, I had the files mixed up. I was writing the larger part to the last file instead of the second one. I need a proofreader for my freakin' code. I replaced the while loop with this and passed:

while (inputStream.available() > 0) {
            int count = inputStream.read(buffer);
            if (count % 2 != 0) {
                outputStream.write(buffer, 0, (count / 2) +1);
                outputStream1.write(buffer, (count / 2)+1 , (count / 2));
            }
            else {
                outputStream.write(buffer, 0, count / 2);
                outputStream1.write(buffer, (count / 2), count / 2);
            }
        }

Mike S

Level 28 , Saint Louis, United States

3 February 2023, 16:12

The first line of write() for each block makes sense to me, Oliver. But I am utterly perplexed why the third argument of the second line goes to count / 2. Shouldn't it be count?? That seems right logically and that's what the lecture content indicates (even though it's not validating my darn submission : /

Thomas

Level 41 , Bayreuth, Germany

3 February 2023, 18:08

you eg have a file (and therefore a buffer) with 11 bytes. The second parameter is the start index inside the buffer, the third specifies how many bytes to write. So if you want to write the first 5 bytes of the buffer, then the arguments are (buffer, 0 , 5). If the file is 11 bytes long and you want to write the 'bigger half', than that bigger half is 'half the file size +1' ( eg. 11 / 2 = 5, 5 + 1 = 6) So the smaller half's size is 5 and the bigger half's size is 6. However you can solve that a little bit smarter.

public static void main(String[] args) throws IOException {

    try (BufferedReader console = new BufferedReader(new InputStreamReader(System.in));
         FileInputStream in = new FileInputStream(console.readLine());
         FileOutputStream out1 = new FileOutputStream(console.readLine());
         FileOutputStream out2 = new FileOutputStream(console.readLine())) {

        byte[] b = new byte[in.available()];
        int half = b.length - b.length / 2;

        in.read(b);

        out1.write(b, 0, half);
        out2.write(b, half, b.length - half);
    }
}

Mike S

Level 28 , Saint Louis, United States

3 February 2023, 19:19

Thanks!

Oliver Heintz

Level 18 , Mustang, United States

8 March 2021, 01:45

Oh, ignore the -1's in my code. It was something else I thought with the positions of the array, I thought.