Thread: Encryption

Ok, I am having an issue with the encryption program I am trying to write.
Basically, I need to have the user enter a string and encrypt it.
I have a variable for the string, an array for the alphabet, and an array for the alphabet reversed.
What I am trying to do is take the string the user entered, compare it to the alphabet array and get a subscript for which letter alphabet array matches the letter in the string. Then, I need to take that subscript of the alphabet array, and compare it to the reversed alphabet array, and assign new letters in the reversed alphabet array to the string, thus "encrypting it"
Essentially, user enters ABC and it becomes ZYX.
Problem is, I have been racking my brain and trying different things, and I cannot fathom a way to do this.
Can anyone help or offer a suggestion?

Can you show us what you've tried?

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.text.*;
import java.util.Random;
 
public class Encrypt extends JFrame
{
    private String dCountry;    //string to hold the destination country
    private String encryptText; //string to hold text for encryption
    private String encryptedText;
    private char temp;
    private char[] Alphabet = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
        'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};
    private char[] Encryption = {'Z', 'Y', 'X' ,'W' , 'V', 'U', 'T', 'S', 'R', 'Q', 'P', 'O', 
        'N', 'M', 'L', 'K', 'J', 'I', 'H', 'G', 'F', 'E', 'D', 'C', 'B', 'A'};
    private JPanel panel;
    private JLabel messageLabel, countryLabel;
    private JTextField input, cInput;
    private JButton encryption;
    private int c = 0;
 
    public void Interface()
    {
        setTitle("Secret");
 
        setSize(300, 200);
 
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
        buildInterface();
 
        add(panel);
 
        setVisible(true);
    }
 
    private void buildInterface()
    {
        messageLabel = new JLabel("Enter Code to be encrypted");
        countryLabel = new JLabel("Enter Destination Country");
 
        input = new JTextField(25);
        cInput = new JTextField(5);
 
        encryption = new JButton("Encrypt");
 
        panel = new JPanel();
 
        panel.add(messageLabel);
        panel.add(input);
        panel.add(countryLabel);
        panel.add(cInput);
        panel.add(encryption);
        encryption.addActionListener(new buttonlistener());
 
    }
 
    private class buttonlistener implements ActionListener
    {
        public void actionPerformed(ActionEvent e)
        {         
            if (e.getSource() == encryption)
            {
                encryptText = input.getText();
                encryptText = encryptText.toUpperCase();
                c = encryptText.length();
                for(int i = 0; i < 26; i++)
                {
                    if (encryptText.charAt(0) == Alphabet[i])
                    {
                        temp = Encryption[i];
                        encryptText.replace(encryptText.charAt(0), temp);
                    }
                }
                System.out.println(temp);
                System.out.println(encryptText);
 
            }
            if (e.getSource() == encryption)
            {
                dCountry = cInput.getText();
                dCountry = dCountry.toUpperCase();
                if(dCountry.equals("FR"))
                {
                    dCountry = "France";
                }
                else if(dCountry.equals("GB"))
                {
                    dCountry = "Great Briton";
                }
                else if(dCountry.equals("CA"))
                {
                    dCountry = "Canada";
                }
                else if(dCountry.equals("JA"))
                {
                    dCountry = "Japan";
                }
                else if(dCountry.equals("RU"))
                {
                    dCountry = "Russia";
                }
                else if(dCountry.equals("GE"))
                {
                    dCountry = "Germany";
                }
                else if(dCountry.equals("AU"))
                {
                    dCountry = "Australia";
                }
                else if(dCountry.equals("MX"))
                {
                    dCountry = "Mexico";
                }
            }
            if(e.getSource() == encryption)
            {
                JOptionPane.showMessageDialog(null,"To: " + dCountry + "\n" + encryptText);
            }
        }
    }
 
}

This is what I have so far. I know my variable temp is getting the proper encryption letter after testing its output, but I cannot seem to replace that one with the one in the string to encrypt the message.

OK, one problem I see is that you may be trying to solve too many problems at once by trying to encrypt with a GUI. I suggest that you isolate the issue that you're currently trying to solve in a small program, and then when you get it to work, put it into the larger program.

Suggestions:

• Make your char arrays constants since you'll never change them. That means that they're declared static final and their names are all upper case.
• You will likely need nested for loops. The outer loop will loop through all the chars in the original text, and the inner loop will loop through the ALPHABET array.
• Make sure that your variable and method naming is compliant with Java naming conventions. All variable and method names should begin with a lower case letter. All class, interface, enum names begin with upper case. Constants are all upper case.

For example your small test class could have a skeleton that looks like this:

class SmallEncrypt {
   // makes these guys constants (static final) and make names all-caps
   private static final char[] ALPHABET = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I',
         'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
         'X', 'Y', 'Z' };
   private static final char[] REVERSE_ALPHABET = { 'Z', 'Y', 'X', 'W', 'V', 'U', 'T', 'S', 'R',
         'Q', 'P', 'O', 'N', 'M', 'L', 'K', 'J', 'I', 'H', 'G', 'F', 'E', 'D',
         'C', 'B', 'A' };
 
   public static void main(String[] args) {
      String originalText = "Hello World";
      String encryptText = "";
 
      for (int i = 0; i < originalText.length(); i++) {
         // get the char at position i
         // change to upper case
         // use inner for loop to find position in ALPHABET array
         // ....
         // encryptText += .... // you have to figure out what goes here
      }
 
      System.out.println("original text: " + originalText);
      System.out.println("encrypted tex: " + encryptText);
   }
}

Ok, I get what your saying there, thank you, that logic is extremely helpful. How might I get it to skip white spaces though, in case I have for instance, a phrase that needs to be encrypted? An if statement using the isWhiteSpace method?

--- Update ---

Never-mind, I just added a white-space char to both arrays, and it seemed to work.

Wonderful, and glad you've got things working!