1// Aim: Program to perform Monoalphabetic cipher (Monoalphabetic Cipher).
2import java.util.*;
3import java.util.Scanner;
4public class mono {
5    private static String alfa = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
6    public static String encrypt(String text ,String key){
7        text.toUpperCase();
8        StringBuilder ct = new StringBuilder();
9        for(char c : text.toCharArray()){
10            int idx = alfa.indexOf(c);
11            if(idx!=-1){
12                ct.append(key.charAt(idx));
13            }
14            else{
15                    ct.append(c);
16            }
17        }
18        return ct.toString();
19    }
20    public static String decrypt(String ct ,String key){
21        ct.toUpperCase();
22        StringBuilder pt = new StringBuilder();
23        for(char c : ct.toCharArray()){
24            int idx = key.indexOf(c);
25            if(idx!=-1){
26                pt.append(alfa.charAt(idx));
27            }
28            else{
29                    pt.append(c);
30            }
31        }
32        return pt.toString();
33    }
34    
35}
36