Why am I not getting the encryption requirement?

Question about the task

Encryption

Java Core, Level 8, Lesson 11

Resolved

The encryption requirement is the only one I'm not getting and I don't know why. Please help.

Come up with an encryption/decryption mechanism.

The program runs with one of the following sets of arguments:
-e fileName fileOutputName -d fileName fileOutputName

where:
fileName is the name of a file to be encrypted/decrypted.
fileOutputName is the name of the file where you need to write the result of the encryption/decryption process.
-e indicates that you need to encrypt the data.
-d indicates that you need to decrypt the data.

Requirements:

You don't need to read anything from the console.
Create an input stream for the file passed as the second argument (fileName).
Create an output stream for the file passed as the third argument (fileOutputName).
In "-e" mode, the program should encrypt fileName and write the result to fileOutputName.
In "-d" mode, the program should decrypt fileName and write the result to fileOutputName.
The file streams must be closed.

package com.codegym.task.task18.task1826; /* Encryption */ import java.io.*; public class Solution { public static void main(String[] args) throws IOException { FileInputStream inputStream = new FileInputStream(args[1]); FileOutputStream outputStream = new FileOutputStream(args[2]); byte[] buffer = new byte[inputStream.available()]; inputStream.read(buffer); if (args[0].equals("-e")){ for(int x : buffer){ x++; } outputStream.write(buffer); } if (args[0].equals("-d")){ for(int y : buffer){ y--; } outputStream.write(buffer); } inputStream.close(); outputStream.close(); } }

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Lisa

Level 41

20 September 2021, 06:01

Hi Mr. Chief, when you change the primitive variables read from the container in a for-each loop, you only change the local variable. It will not be written back automatically somehow. If values in the container are to be changed, you could consider a normal loop (to verify this just output the array before writing back or compare the two files). Yeah, yeah 🤪😜

The Chief

Level 18 , United States

20 September 2021, 22:55

Hi Lisa, I tried using a normal loop but it still wouldn't work. Can you show me how the normal loop should look in my code?

Lisa

Level 41

21 September 2021, 08:05

sure, have a look....

byte[] buffer = "abc".getBytes();
for (int x : buffer)
    x++; // local variable x incemented, result never used
for (int c : buffer) System.out.print((char) c);

System.out.println();
for (int i = 0; i < buffer.length; i++)
    buffer[i]++; // index[i] changed in array
for (int c : buffer) System.out.print((char) c);

That's the way to go... or just read, change and write directly without using an array, yeah, yeah 😜🤪

The Chief

Level 18 , United States

22 September 2021, 03:02

Okay, I got it now. Thank you.