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Decryption.java
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Decryption.java
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import java.util.Scanner;
public class Decryption{
public static void main(String[] args) {
String S="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
String s="abcdefghijklmnopqrstuvwxyz";
Scanner sc=new Scanner(System.in);
System.out.println("Enter the Cipher text");
String ciphertext=sc.nextLine();
System.out.println("Enter the secret key");
int key=sc.nextInt();
String plaintext="";
for(int i=0;i<ciphertext.length();i++){
char a=ciphertext.charAt(i);
int b=0;
if(Character.isUpperCase(a)){
b=(S.indexOf(a)-key)%26;
if(b<0)
plaintext+=S.charAt(b+26);
else
plaintext+=S.charAt(b);
}
else{
b=(s.indexOf(a)-key)%26;
if(b<0)
plaintext+=s.charAt(b+26);
else
plaintext+=s.charAt(b);
}
}
System.out.println("Plain text is "+plaintext);
}
}