MD5 Decrypter [Demo chữ]

package demo;

import java.awt.Component;
import java.awt.Desktop;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.math.BigInteger;
import java.net.URI;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JOptionPane;
import javax.swing.JTextField;

public class GiaiChu extends JFrame implements ActionListener {

    private GridBagLayout gb;
    private GridBagConstraints gbc;
    private JLabel lbForm, lbUser, lbPass, lbView;
    private JTextField tfUser, tfPass;
    private JButton btRegister, btCancel;
    JMenuBar mymbar;
    JMenu jmFile, jmHelp;

    private static String encryptMD5(String input) {
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            byte[] messageDigest = md.digest(input.getBytes());
            BigInteger number = new BigInteger(1, messageDigest);
            String hashtext = number.toString(16);
            while (hashtext.length() < 32) {
                hashtext = "0" + hashtext;
            }
            return hashtext;
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
    }

    public void Them(Component comp, int x, int y, int rong, int cao) {
        gbc = new GridBagConstraints();
        gbc.gridx = x;
        gbc.gridy = y;
        gbc.gridwidth = rong;
        gbc.gridheight = cao;
        gb.setConstraints(comp, gbc);
        this.add(comp);
    }

    private void setMenu() {
        mymbar = new JMenuBar();
        jmFile = new JMenu("File");
        JMenuItem exit = new JMenuItem("Exit");
        exit.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.exit(0);
            }
        });
        jmFile.add(exit);
        mymbar.add(jmFile);

        jmHelp = new JMenu("Help");
        JMenuItem creator = new JMenuItem("Author");
        creator.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                JOptionPane.showMessageDialog(null, "Author: Thieu Mao - KSEC");
            }
        });
        JMenuItem instruction = new JMenuItem("Website");
        instruction.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                Desktop desktop = Desktop.getDesktop();
                try {
                    desktop.browse(new URI("http://thieumao.blogspot.com/"));
                } catch (Exception ex) {
                    System.out.println("Error!");
                }
            }
        });
        jmHelp.add(creator);
        jmHelp.addSeparator();
        jmHelp.add(instruction);
        mymbar.add(jmHelp);

        setJMenuBar(mymbar);
    }

    public GiaiChu(String title) {
        super(title);
        this.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent we) {
                if (JOptionPane.showConfirmDialog(null, "Are you sure ?") == JOptionPane.OK_OPTION) {
                    System.exit(0);
                }
                setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
            }
        });

        setMenu();

        lbForm = new JLabel("MD5 Decrypter");
        lbUser = new JLabel("MD5:");
        lbPass = new JLabel("Text:");
        tfUser = new JTextField(35);
        tfPass = new JTextField(35);
        tfPass.disable();
        btRegister = new JButton("Calculate");
        btCancel = new JButton("Clear");

        gb = new GridBagLayout();
        this.setLayout(gb);
        Them(lbForm, 1, 0, 2, 1);
        Them(lbUser, 0, 1, 1, 1);
        Them(tfUser, 1, 1, 2, 1);
        Them(lbPass, 0, 2, 1, 1);
        Them(tfPass, 1, 2, 2, 1);
        Them(btRegister, 1, 3, 1, 1);
        Them(btCancel, 2, 3, 1, 1);

        btRegister.addActionListener(this);
        btCancel.addActionListener(this);
    }

    public static void main(String[] args) throws Exception {
        GiaiChu fr = new GiaiChu("MD5 Decrypter  - Thieu Mao");
        fr.setSize(500, 200);
        fr.setVisible(true);
    }

    @Override
    public void actionPerformed(ActionEvent ae) {
        if (ae.getSource() == btRegister) {

            char chStart = 'a';
            char chEnd = 'z';

            String str;
            boolean check = true;
            // 1 ki tu
            char i0 = chStart;
            while (check && i0 <= chEnd) {
                str = String.valueOf(i0);
                System.out.println(str);
                if (encryptMD5(str).equals(tfUser.getText())) {
                    tfPass.setText(str);
                    check = false;
                }
                i0++;
            }
            // 2 ki tu
            i0 = chStart;
            while (check && i0 <= chEnd) {
                char i1 = chStart;
                while (check && i1 <= chEnd) {
                    str = String.valueOf(i0) + String.valueOf(i1);
                    System.out.println(str);
                    if (encryptMD5(str).equals(tfUser.getText())) {
                        tfPass.setText(str);
                        check = false;
                    }
                    i1++;
                }
                i0++;
            }
            // 3 ki tu
            i0 = chStart;
            while (check && i0 <= chEnd) {
                char i1 = chStart;
                while (check && i1 <= chEnd) {
                    char i2 = chStart;
                    while (check && i2 <= chEnd) {
                        str = String.valueOf(i0) + String.valueOf(i1) + String.valueOf(i2);
                        System.out.println(str);
                        if (encryptMD5(str).equals(tfUser.getText())) {
                            tfPass.setText(str);
                            check = false;
                        }
                        i2++;
                    }
                    i1++;
                }
                i0++;
            }
            // 4 ki tu
            i0 = chStart;
            while (check && i0 <= chEnd) {
                char i1 = chStart;
                while (check && i1 <= chEnd) {
                    char i2 = chStart;
                    while (check && i2 <= chEnd) {
                        char i3 = chStart;
                        while (check && i3 <= chEnd) {
                            str = String.valueOf(i0) + String.valueOf(i1) + String.valueOf(i2) + String.valueOf(i3);
                            System.out.println(str);
                            if (encryptMD5(str).equals(tfUser.getText())) {
                                tfPass.setText(str);
                                check = false;
                            }
                            i3++;
                        }
                        i2++;
                    }
                    i1++;
                }
                i0++;
            }
            // 5 ki tu
            i0 = chStart;
            while (check && i0 <= chEnd) {
                char i1 = chStart;
                while (check && i1 <= chEnd) {
                    char i2 = chStart;
                    while (check && i2 <= chEnd) {
                        char i3 = chStart;
                        while (check && i3 <= chEnd) {
                            char i4 = chStart;
                            while (check && i4 <= chEnd) {
                                str = String.valueOf(i0) + String.valueOf(i1) + String.valueOf(i2) + String.valueOf(i3) + String.valueOf(i4);
                                System.out.println(str);
                                if (encryptMD5(str).equals(tfUser.getText())) {
                                    tfPass.setText(str);
                                    check = false;
                                }
                                i4++;
                            }
                            i3++;
                        }
                        i2++;
                    }
                    i1++;
                }
                i0++;
            }
            // 6 ki tu
            i0 = chStart;
            while (check && i0 <= chEnd) {
                char i1 = chStart;
                while (check && i1 <= chEnd) {
                    char i2 = chStart;
                    while (check && i2 <= chEnd) {
                        char i3 = chStart;
                        while (check && i3 <= chEnd) {
                            char i4 = chStart;
                            while (check && i4 <= chEnd) {
                                char i5 = chStart;
                                while (check && i5 <= chEnd) {
                                    str = String.valueOf(i0) + String.valueOf(i1) + String.valueOf(i2) + String.valueOf(i3) + String.valueOf(i4) + String.valueOf(i5);
                                    System.out.println(str);
                                    if (encryptMD5(str).equals(tfUser.getText())) {
                                        tfPass.setText(str);
                                        check = false;
                                    }
                                    i5++;
                                }
                                i4++;
                            }
                            i3++;
                        }
                        i2++;
                    }
                    i1++;
                }
                i0++;
            }

        }
        if (ae.getSource() == btCancel) {
            tfUser.setText("");
            tfPass.setText("");
        }
    }
}