Create MonoAlphabetic.java

Author: riti2601

src/main/java/com/thealgorithms/ciphers/MonoAlphabetic.java

@@ -0,0 +1,79 @@
+package MonoAlphabetic_Cipher;
+import java.util.Scanner;
+
+public class MonoAlphabetic {
+    public static void main(String[] args) {
+        Scanner read = new Scanner(System.in);
+        System.out.println("Hello User! \nEnter your name:");
+        String name = read.nextLine();
+        read.nextLine();
+
+        System.out.println("Welcome "+name+"!\nDo you want to encrypt data or decrypt the data?\nFor encryption enter: 1\nFor decryption enter: 2");
+        int x = read.nextInt();
+        read.nextLine();
+
+        String key = "MNBVCXZLKJHGFDSAPOIUYTREWQ";
+
+        switch (x) {
+            case 1:
+                System.out.println("\nPlease enter the data that is to be encrypted, we will be using MonoAlphabetic Cipher to encrypt the data.");
+                String data = read.nextLine().toUpperCase();;
+                
+                String encryptedData = encrypt(data,key);
+                System.out.println("Encrypted data: " + encryptedData);
+                break;
+            
+            case 2:
+                System.out.println("\nPlease enter the data that is to be decrypted, we will be using MonoAlphabetic Cipher to decrypt the data.");
+                data = read.nextLine().toUpperCase();;
+                
+                String decryptedData = decrypt(data,key);
+                System.out.println("Decrypted data: " + decryptedData);
+                break;
+        
+            default:
+                System.out.println("The input was invalid. Kindly restart.");
+                break;
+        }
+
+        
+    }
+
+    public static String encrypt(String data, String key){
+        int idx;
+        char c;
+        StringBuffer sb = new StringBuffer(data);
+
+        for(int i=0; i<sb.length(); i++){
+            idx = sb.charAt(i)-65;
+            c = key.charAt(idx);
+            sb.setCharAt(i, c);
+        }
+        return new String(sb);
+    }
+
+    public static String decrypt(String data, String key){
+        int idx;
+        char c;
+        StringBuffer sb = new StringBuffer(data);
+
+        for(int i=0; i<sb.length(); i++){
+            c = sb.charAt(i);
+            idx = getIndex(c,key);
+            c = (char) (idx + 65);
+            sb.setCharAt(i, c);
+        }
+        return new String(sb);
+    }
+
+    public static int getIndex(char c, String key){
+        int idx = -1;
+        for(int i=0; i<key.length();i++){
+            if(key.charAt(i) == c){
+                idx = i;
+            }
+        }
+        return idx;
+    }
+
+}