I am tired trying and trying without result. I need help please. I could not find out the solution

Question about the task

Encryption

Java Core, Level 8, Lesson 11

Resolved

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.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.util.Base64; public class Solution { public static void main(String[] args) throws IOException { String fileName = args[1]; String fileOutPutName = args[2]; FileInputStream fileIn = new FileInputStream(fileName); FileOutputStream fileOut = new FileOutputStream(fileOutPutName); switch (args[0]) { case "-e": byte[] buffer = new byte[fileIn.available()]; while (fileIn.available() > 0) { byte data = (byte)fileIn.read(buffer); fileOut.write(data); } for (byte b: buffer) System.out.print(b + " "); fileOut.close(); fileIn.close(); break; case "-d": while (fileIn.available() > 0) { int data = fileIn.read(); fileOut.write(data); } fileOut.close(); fileIn.close(); break; } } }

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Ewerton Backend Developer

4 July 2019, 16:28

In the "-d" case, you didn't decrypt your file, you only read&write it. A suggestion: one of the simplest encryption mechanisms is the Caesar cipher, where you just take some "byte" and shift by some value, e.g.: a -> b [97] -> [98] For encryption, you can read the byte and write (byte+1). For decryption, you can read the byte and write (byte-1).

Daniel Walbolt

Level 22 , Waterville, United States

26 July 2020, 13:59

or be a real trickster and make sure the code doesn't go above 127 and below 0 ;) because that way it's always a character and not a negative number.

Sela

Level 20 , Poland

18 September 2020, 10:37

narrowing bytes to range of <0, 127> would restrict files only to text ones. what about binaries? isn't it better to restrict the value to the range of byte primitive i.e. <-128, 127>?