explanation

Question sur la mission

Inversion d'un fichier

Bases de Java, Niveau 8, Leçon 5

Résolues

could someone explain me what's wrong ??

package fr.codegym.task.task18.task1809; /* Inversion d'un fichier */ import java.io.*; public class Solution { public static void main(String[] args) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String S = reader.readLine(); String A = reader.readLine(); FileOutputStream fileOutputStream = new FileOutputStream(A); FileInputStream fileInputStream = new FileInputStream(S); while (fileInputStream.available() > 0) { byte[] bytes = new byte[fileInputStream.available()]; for (int i = 0; i < fileInputStream.available(); i++) { bytes[i] = (byte) fileInputStream.read(); } // fermeture des flux // for(int i=0; i < fileInputStream.available(); i++){ fileOutputStream.write(bytes[fileInputStream.available()-1-i]); } } fileInputStream.close(); fileOutputStream.close(); } }

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Guadalupe Gagnon

niveau Tampa, Tampa, United States

31 décembre 2020, 17:27

solution

Have you tested the code to ensure that, in each step, it does exactly what you want it to do? At this level you should be doing this with single every task. Also, you should be notating your code before asking questions so that we know what your intentions are. Without knowing what you intend to do we aren't able to explain where an error in understanding is occurring. *hint* what does fileInputStream.available() return?

Banak

niveau Saint-Gratien, Saint-Gratien, France

31 décembre 2020, 17:40

import java.io.*; public class Solution { public static void main(String[] args) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String S = reader.readLine(); String A = reader.readLine(); // define flows // FileOutputStream fileOutputStream = new FileOutputStream(A); FileInputStream fileInputStream = new FileInputStream(S); // create the byte array to be read and fill it // while (fileInputStream.available() > 0) { byte[] bytes = new byte[fileInputStream.available()]; for (int i = 0; i < fileInputStream.available(); i++) { bytes[i] = (byte) fileInputStream.read(); } // Write the elements in the table in reverse order.in the second file // for(int i=0; i < fileInputStream.available(); i++){ fileOutputStream.write(bytes[fileInputStream.available()-1-i]); } } fileInputStream.close(); fileOutputStream.close(); }

Banak

niveau Saint-Gratien, Saint-Gratien, France

31 décembre 2020, 17:45

solution

ok " fileInputStream.available() " Apparently I used this command twice that's why he hasn't got anything to write anymore. Thank you for this indication ..;

Guadalupe Gagnon

niveau Tampa, Tampa, United States

31 décembre 2020, 17:48

solution

Yes! The problem is that IS.available() returns how many bytes are left to be read, not how many bytes are in the file. So for each byte that you read, that number gets smaller. Both for loops work as long as i is less that IS.available(), which won't work. The first loop will only read half the bytes as IS.available() ticks down with each byte read until i is equal to or greater than it. The second loop will write half the bytes saved, but because it is backwards will only write the second half of the byte[] which hasn't had any bytes put into it. This will result in the default value of 0 being written to the output file as many times as half the original length of the input file.