Please help!! One condition doesn't satisfy

Question about the task

Splitting a file

Java Core, Level 8, Lesson 5

Resolved

I dont understand were I am wrong in writing in the second file

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(); FileInputStream firstFile = new FileInputStream(file1); FileOutputStream secondFile = new FileOutputStream(file2); FileOutputStream thirdFile = new FileOutputStream(file3); int count = 0; int[] buffer = new int[firstFile.available()]; while(firstFile.available() > 0){ int data = firstFile.read(); buffer[count] = data; count++; } if(buffer.length % 2 > 0){ for (int i = 0; i<(buffer.length/2) +1 ; i++){ secondFile.write(buffer[i]); } for (int i = (buffer.length/2) ; i<((buffer.length/2) + 1)-buffer.length; i++){ thirdFile.write(buffer[i]); } } else { for (int i = 0; i <(buffer.length / 2); i++) { secondFile.write(buffer[i]); } for (int i = (buffer.length / 2); i < (buffer.length / 2);i++){ thirdFile.write(buffer[i]); } } reader.close(); firstFile.close(); secondFile.close(); thirdFile.close(); } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

15 June 2020, 15:11

Lines 37-39 are adding one extra byte in the second file that should not be there. Next line 40 wont work because the break clause (the second expression in the for loop) will end up with a negative number. The second expressions says: i < ((buffer.length/2) + 1) - buffer.length Take for example if the buffer was length 15. This would mean that the numbers would be: i < (7 + 1) - 15 ----→ i < 8 - 15 ----→ i < -7 This would break the the loop before it even did one cycle. Next line 48 will not work because the code is setting i to the value of the break clause in the if statement, so if the buffer were 16, line 48 would read:

for(int i = 8; i < 8; i++) {
  // code in here would not run because loop would break at first cycle
}

Guadalupe Gagnon

Level 37 , Tampa, United States

15 June 2020, 15:17

The math for this task is extremely simple. By dividing the amount of total bytes in the buffer by two you will always arrive at the correct amount of bytes to put in the second file. So if the buffer were 10, dividing by two would equal 5 and that is how many bytes go in the second file. The remainder of 5 bytes go in the third file. If the amount of bytes were 11, dividing by two would equal 5 which is the amount of bytes that go into the second file. The remainder of 6 would go in the third file. You can do that for any number of total bytes: divide by two to get the amount of bytes that go in the second file while the remainder goes into the third file.

David

Level 26 , Bucharest, Romania

15 June 2020, 16:27

Yeah, I understand, i was overcomplicating the things...I dont know why. Now returning to the task it is a lot clearer, I am wondering what I was trying to do :))) ...but never mind. But why are you saying that : "Lines 37-39 are adding one extra byte in the second file that should not be there"?? Isn't this one of the condition to add the larger part to second file?

Guadalupe Gagnon

Level 37 , Tampa, United States

15 June 2020, 18:16

Yes, you are correct about the second file being the larger, I made a mistake there in reading the requirements. So to amend my answer above a little bit: divide by 2 to get the amount to go into the third file while the remainder goes into the second file.

David

Level 26 , Bucharest, Romania

15 June 2020, 20:41

It's ok. It helped me a lot anyway! Thank you!