Error: Could not find or load main class AffineCipher

Question

I am trying to create an encryption and decryption program but when I run there is an error. I tried to run my program on Intelli J ide, I also tried on Eclipse but also got the same error, where did I go wrong?

package com.sanfoundry.setandstring;

import java.util.Scanner;

public class AffineCipher
{

    public static String encryptionMessage(String Msg)
    {
        String CTxt = "";
        int a = 3;
        int b = 6;
        for (int i = 0; i < Msg.length(); i++)
        {
            CTxt = CTxt + (char) ((((a * Msg.charAt(i)) + b) % 26));
        }
        return CTxt;
    }

    public static String decryptionMessage(String CTxt)
    {
        String Msg = "";
        int a = 3;
        int b = 6;
        int a_inv = 0;
        int flag = 0;
        for (int i = 0; i < 26; i++)
        {
            flag = (a * i) % 26;
            if (flag == 1)
            {
                a_inv = i;
                System.out.println(i);
            }
        }
        for (int i = 0; i < CTxt.length(); i++)
        {
            Msg = Msg + (char) (((a_inv * ((CTxt.charAt(i) - b)) % 26)));
        }
        return Msg;
    }
    public static void main(String[] args)
    {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter the message: ");
        String message = sc.next();
        System.out.println("Message is :" + message);
        System.out.println("Encrypted Message is : "
                + encryptionMessage(message));
        System.out.println("Decrypted Message is: "
                + decryptionMessage(message));
        sc.close();
    }


}