I don't think I understand what void write(byte[] buff,int form, int count) is doing.

Question about the task

Splitting a file

Java Core, Level 8, Lesson 5

Resolved

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.*; public class Solution { public static void main(String[] args) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); FileInputStream fis = new FileInputStream(reader.readLine()); FileOutputStream fos_1 = new FileOutputStream(reader.readLine()); FileOutputStream fos_2 = new FileOutputStream(reader.readLine()); byte[] buffer = new byte[fis.available()]; while(fis.available() > 0) { int count = fis.read(buffer); if(fis.available() % 2 == 0) { fos_1.write(buffer, 0, count/2); fos_2.write(buffer, count/2, count/2); } else { fos_1.write(buffer, 0, count -(count/2)); fos_2.write(buffer, count-(count/2), (count/2)); } } reader.close(); fis.close(); fos_1.close(); fos_2.close(); } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

25 October 2023, 03:22

solution

The problem is that this code reads everything available from file1 on line 23. Because of this on line 24 calling fis.available() results in 0 every time. That is a bug in the code and the rest of the algorithm will be wrong because of it. Tip: If you take an array and divide its length by 2 you end up with the smaller half size every time. This is because it will either be exactly half if the length of the array is an even number or, when the number is odd, it will result in a slightly smaller than half number because the .5 will be dropped. For example dividing 7 by 2 in java results in 3. Diving 35 results in 17 etc. When you figure out the smaller half you can simply just subtract that number by the total length to get the larger half size. For example, if the length is 7 and you divide by 2 you get 3. Subtract 7 by 3 and you get 4, which is the size of the larger half. 35 divided by 2 is 17 and when you subtract that from 35 your get 18. You can simply figure these out and shorten your code by 6 lines:

int small = buffer.length / 2;
int large = buffer.length - small;
fos_1.write(buffer, 0, small);
fos_2.write(buffer, small, large);

FelixUjo

Level 35 , Gijón, Spain

26 October 2023, 20:27

Solved, thanks.