the program appears to work as per requirements but wont pass the validation (again !!) . any insight please. many thanks

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the program appears to work as per requirements but wont pass the validation (again !!) . any insight please. many thanks

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 fileInputStream = new FileInputStream(new File(args[1])); FileOutputStream fileOutputStream = new FileOutputStream(new File(args[2])); switch (args[0]) { case "-e": //encyption while (fileInputStream.available()>0){ fileOutputStream.write(fileInputStream.read()+1); } break; case "-d": //decryption while (fileInputStream.available()>0){ fileOutputStream.write(fileInputStream.read()-1); } break; } fileInputStream.close(); fileOutputStream.close(); } }

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horst

Level 26 , Not in list

6 October 2020, 16:12

I'm not 100% sure, but I used a similar approach and had a similar problem: Just like you, I added some int value to the byte for encryption, and I subtracted the same int value for decryption. However, what happened in my code was the following: Let's say, the file we are reading is a text file and starts with the capital letter "C", which has a decimal value of 67. Now if you add 1 to it, the letter "C" is casted/represented as its decimal number in order to be able to add 1 and we end up with the int value 68. So it has become an int and is not a byte anymore. Now for writing/decryption, we subtract 1 and come back to 67. However, in my case, the value 67 was not automatically casted back to the byte representing 67 (the letter "C"), but the int value 67 was written to my file (instead of "C"). I ended up with documents that had just a bunch of numbers in them. A simple explicit typecasting did do the trick in my case, so I think it is worth a try to cast your int back to a byte before writing it to the file.

Lgd

Level 20 , London, United Kingdom

7 October 2020, 08:33

hello horst...tks for your comments so I tried this...I think it's what you meant. it appears the same as before - i.e. it the program appears to work but it wont pass validation. I'll stick with it and let you know if figure it out ! thanks again package com.codegym.task.task18.task1826; /* Encryption */ import java.io.*; public class Solution { public static void main(String[] args) throws IOException { FileInputStream fileInputStream = new FileInputStream(new File(args[1])); FileOutputStream fileOutputStream = new FileOutputStream(new File(args[2])); String mode = args[0]; switch (mode) { case "-e": //encyption while (fileInputStream.available()>0){ fileOutputStream.write((byte) (fileInputStream.read()+1)); } break; case "-d": //decryption while (fileInputStream.available()>0){ fileOutputStream.write((byte) (fileInputStream.read()-1)); } break; } fileInputStream.close(); fileOutputStream.close(); } }

Lgd

Level 20 , London, United Kingdom

7 October 2020, 11:59

It seems all I had to do was make this change...I still to look at it more closely to understand why this makes a difference FileInputStream fileInputStream = new FileInputStream(args[1]); FileOutputStream fileOutputStream = new FileOutputStream(args[2]);

horst

Level 26 , Not in list

7 October 2020, 15:36

I'm glad you found a solution. Admittedly, I am not an expert in FileInput/OutputStreams, but at least to my eye, the two constructors FileInputStream(File file) and FileInputStream(String filename) do not make a real difference in the documentation. So I didn't even notice/recognize that this could actually make a difference. Maybe this is more of a CodeGym-validation-specific thing rather than an actual error in your code. Chapeau for even considering this as an issue!

Nouser

Level 36 , Germany

6 October 2020, 14:50

? perhaps shifting just one byte isn't sufficient for validation Is there a slight possibility that your keyboard is cursed somehow?