Login.java

import java.awt.CardLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.StringTokenizer;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;


public class Login extends JPanel implements ActionListener{
    JLabel userL = new JLabel("Username: ");
    JTextField userTF = new JTextField();
    JLabel passL = new JLabel("Password: ");
    JPasswordField passTF = new JPasswordField();
    JPanel loginP = new JPanel(new GridLayout(3, 2));
    JPanel panel = new JPanel();
    JButton login = new JButton("Login");
    JButton register = new JButton("Register");
    CardLayout cl;
    Login(){
        setLayout(new CardLayout());
        loginP.add(userL);
        loginP.add(userTF);
        loginP.add(passL);
        loginP.add(passTF);
        login.addActionListener(this);
        register.addActionListener(this);
        loginP.add(login);
        loginP.add(register);
        panel.add(loginP);
        add(panel, "login");
        cl = (CardLayout) getLayout();
    }


    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == login){
            try {
                BufferedReader input = new BufferedReader(new FileReader("passwords.txt"));
                String pass = null;
                String line = input.readLine();
                while(line != null){
                    StringTokenizer st = new StringTokenizer(line);
                    if(userTF.getText().equals(st.nextToken()));
                        pass = st.nextToken();
                        line = input.readLine();
                }
                input.close();
                MessageDigest md = MessageDigest.getInstance("SHA-256");
                md.update(new String(passTF.getPassword()).getBytes());
                byte byteData[] = md.digest();
                StringBuffer sb = new StringBuffer();
                for(int i = 0; i < byteData.length; i++)
                    sb.append(Integer.toString((byteData[i] & 0xFF) + 0x100, 16).substring(1));
                if(pass.equals(sb.toString()))
                    add(new FileBrowser(userTF.getText()), "fb");
                    cl.show(this, "fb");
            } catch (FileNotFoundException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            } catch (NoSuchAlgorithmException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
        }
        if(e.getSource() == register){
            add(new Register(), "register");
            cl.show(this, "register");
        }
    }
    public static void main(String[] args){
        JFrame frame = new JFrame("Text Editor");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(500, 500);
        Login login = new Login();
        frame.add(login);
        frame.setVisible(true);
    }

}