This uses keyword substitution cryptography. Encodes and decodes a text string

KeywordCipher.java

/**
 * @tbenjis
 * Keyword substitution cryptography
 * Author: tunde
 * 
 * */

import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JOptionPane;
import javax.swing.JTextPane;
import javax.swing.JTextField;
import javax.swing.JButton;
import javax.swing.JLabel;

import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class KeywordCipher extends JFrame implements ActionListener {

	private JPanel contentPane;
	private JTextField keytxt;
	private JButton btnEncode;
	private JButton btnDecode;

	private String values = "abcdefghijklmnopqrstuvwxyz ";
	private JTextPane textPaneInput;
	private JTextPane textPaneOutput;

	/**
	 * Launch the application.
	 */
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					KeywordCipher frame = new KeywordCipher();
					frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}

	/**
	 * Create the frame.
	 */
	public KeywordCipher() {
		setResizable(false);
		setTitle("Keyword Cipher");
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setBounds(100, 100, 529, 346);
		contentPane = new JPanel();
		contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
		setContentPane(contentPane);
		contentPane.setLayout(null);

		textPaneInput = new JTextPane();
		textPaneInput.setBounds(10, 28, 497, 90);
		contentPane.add(textPaneInput);

		textPaneOutput = new JTextPane();
		textPaneOutput.setBounds(10, 207, 497, 90);
		contentPane.add(textPaneOutput);

		keytxt = new JTextField();
		keytxt.setBounds(124, 151, 158, 20);
		contentPane.add(keytxt);
		keytxt.setColumns(10);

		btnEncode = new JButton("Encode");
		btnEncode.setBounds(292, 150, 89, 23);
		contentPane.add(btnEncode);

		btnDecode = new JButton("Decode");
		btnDecode.setBounds(391, 150, 89, 23);
		contentPane.add(btnDecode);

		JLabel lblKey = new JLabel("Keyword:");
		lblKey.setFont(new Font("Tahoma", Font.BOLD, 11));
		lblKey.setBounds(36, 154, 78, 14);
		contentPane.add(lblKey);

		JLabel lblText = new JLabel("Text:");
		lblText.setFont(new Font("Tahoma", Font.BOLD, 11));
		lblText.setBounds(10, 11, 46, 14);
		contentPane.add(lblText);

		JLabel lblOutput = new JLabel("Output:");
		lblOutput.setFont(new Font("Tahoma", Font.BOLD, 11));
		lblOutput.setBounds(10, 189, 46, 14);
		contentPane.add(lblOutput);

		btnDecode.addActionListener(this);
		btnEncode.addActionListener(this);
	}

	@Override
	public void actionPerformed(ActionEvent e) {
		// TODO Auto-generated method stub

		if (e.getSource() == btnEncode) {
			if (keytxt.getText().matches("[a-zA-Z]+"))
				textPaneOutput.setText(Encode(textPaneInput.getText(),
						keytxt.getText()));
			else
				JOptionPane.showMessageDialog(this, "Enter letters only");

		}

		if (e.getSource() == btnDecode) {
			if (keytxt.getText().matches("[a-zA-Z]+"))
				textPaneOutput.setText(Decode(textPaneInput.getText(),
						keytxt.getText()));
			else
				JOptionPane.showMessageDialog(this, "Enter letters only");
		}

	}

	private String Encode(String text, String key) {
		char charEnc;
		int valEnc;
		char newEnc;
		String encrypted = "";
		key = key.toLowerCase();
		text = text.toLowerCase();
		//replace repeated characters in key
		key = key.replaceAll("(.)(?=.*\\1)", "");
		String newValue = key;
		// loop the value and add the rest to newValue
		for (int i = 0; i < values.length(); i++) {
			charEnc = values.charAt(i);
			// check if char exixt in the new key
			if (newValue.indexOf(charEnc) < 0) {				
				// add the char to new key if is not there
				newValue += values.charAt(i);
			}
		}

		// now loop through the string
		for (int i = 0; i < text.length(); i++) {
			charEnc = text.charAt(i);
			// check the index of the character at the main values string
			valEnc = values.indexOf(charEnc);
			// pick the character of the corresponding newvalue index
			newEnc = newValue.charAt(valEnc);
			encrypted += newEnc;
		}
		return encrypted.toUpperCase();
	}

	private String Decode(String text, String key) {
		char charEnc;
		int valEnc;
		char newEnc;
		String decrypted = "";
		key = key.toLowerCase();
		text = text.toLowerCase();
		//replace repeated characters in key
		key = key.replaceAll("(.)(?=.*\\1)", "");
		String newValue = key;

		// loop the value and add the rest to newValue
		for (int i = 0; i < values.length(); i++) {
			charEnc = values.charAt(i);
			// check if char exixt in the new key
			if (newValue.indexOf(charEnc) < 0) {
				// add the char to new key if is not there
				newValue += values.charAt(i);
			}
		}

		// now loop through the string
		for (int i = 0; i < text.length(); i++) {
			charEnc = text.charAt(i);
			// check the index of the character at the main values string
			valEnc = newValue.indexOf(charEnc);
			// pick the character of the corresponding newvalue index
			newEnc = values.charAt(valEnc);
			decrypted += newEnc;
		}
		return decrypted.toUpperCase();
	}
}