//Encrytion of text

import java.util.Scanner;

public class Decryption //File name

{

public static void main(String... args)

{

Scanner ipt = new Scanner(System.in);

System.out.print("Enter Encrypted message : ");

String input = ipt.nextLine();

StringBuilder Decrypt = new StringBuilder(input);

String lower_alpha = "abcdefghijklmnopqrstuvwxyz"; //If the character is lower cipher converts into lower actual text

String upper_alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; //If the character is upper cipher converts into upper actual text

String upper_converted_text="",lower_converted_text="";

System.out.print("Enter a private key : ");

int private_key = ipt.nextInt();

upper_converted_text = upper_alpha.substring(private_key)+upper_alpha.substring(0,private_key); //Shifting the lower case alphabets using private key

lower_converted_text = lower_alpha.substring(private_key)+lower_alpha.substring(0,private_key); //Shifting the upper case alphabest using private key

System.out.println("Message before decryption : "+Decrypt);

//Converting the cipher text into actual text.

for(int chr=0;chr<Decrypt.length();chr++)

{

char pointer = Decrypt.charAt(chr);

//If the character is upper case

if(Character.isUpperCase(pointer))

{

int index = upper_converted_text.indexOf(pointer);

if(index!=-1)

{

char new_pointer = upper_alpha.charAt(index);

Decrypt.setCharAt(chr,new_pointer);

}

}

//If the character is lower case

else if(Character.isLowerCase(pointer))

{

int index = lower_converted_text.indexOf(pointer);

if(index!=-1)

{

char new_pointer = lower_alpha.charAt(index);

Decrypt.setCharAt(chr,new_pointer);

}

}

}

System.out.println("Message after decryption : "+Decrypt);

}

}