Question

Needs to be in basic JAVA

Write a program that does basic encrypting of text. You will ask the user the filename of a text file that contains a few sentences of text. You will read this text file one character at a time, and change each letter to another one and write out to an output file. The conversion should be done a -> b, b->c , … z->a, A->B, B->C, …. Z->A. This means just shift each letter by one, but Z goes back to A.

Example: Hello converts to Ifmmp

All other punctuation and spaces or symbols can stay as they are.  

If you have time you could write the reverse program that would take your encrypted file as the input and get back the original message

Answer 1

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class EncryptDecrypt
{
   public static void encrypt(String inFile, String outFile) throws IOException {
       File f=new File(inFile); //Creation of File Descriptor for input file
   FileReader fr=new FileReader(f); //Creation of File Reader object
  
   //creating file writer object
   FileWriter fw = new FileWriter(new File(outFile));
   BufferedReader br=new BufferedReader(fr); //Creation of BufferedReader object
   int c = 0;   
   while((c = br.read()) != -1) //Read char by Char
   {
       //shifting by 1
           int ch = c;
           //checkking if upper case or lower case and converting accordingly
           if(Character.isUpperCase(ch)) {
               ch = ((c+1)-65 ) % 26 + 65;
           } else if(Character.isLowerCase(ch)) {
               ch = ((c+1)-97 ) % 26 + 97;
           }
   char character = (char) ch; //converting integer to char
   //qriting to output file
   fw.append(character);
   }
  
   br.close();
   fw.close();
   }
  
   public static void decrypt(String file) throws IOException {
       File f=new File(file); //Creation of File Descriptor for input file
   FileReader fr=new FileReader(f); //Creation of File Reader object
  
   BufferedReader br=new BufferedReader(fr); //Creation of BufferedReader object
   int c = 0;   
   while((c = br.read()) != -1) //Read char by Char
   {
       //shifting by 1
       int ch = c;
          
           if(Character.isUpperCase(ch)) {
               ch = ((c-1)-65 ) % 26 + 65;
           } else if(Character.isLowerCase(ch)) {
               ch = ((c-1)-97 ) % 26 + 97;
           }
   char character = (char) ch; //converting integer to char
   System.out.print(character);
   }
  
   br.close();
   }
public static void main(String[] args) throws IOException
{
encrypt("D://input.txt", "D://output.txt");
decrypt("D://output.txt");
  
}
}