Login System with Database

Database.java

import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;

public class Database {
	
	/*
	 * Create a text file first named "Account.txt" and fill in some usernames and passwords
	 */
	
	private String fileName;
	private File myFile;
	private FileReader fRead;
	private FileWriter fWrite;
	private Scanner scan;
	
	public Database() {
		fileName = "Account.txt";
		myFile = new File(fileName);
	}
	public Database(String fileName) {
		this.fileName = fileName;
		myFile = new File(fileName);
	}
	public void setFileName(String fileName) throws IOException {
		this.fileName = fileName;
		myFile = new File(fileName);
		if(myFile.exists()) {
			System.err.println("File already exist.");
		}
		else {
			fWrite = new FileWriter(fileName);
		}
	}
	public String getFileName() { return fileName; }
	public boolean isValid(String un, String pwd) {
		boolean valid = false;
		try {
			fRead = new FileReader(myFile);
			scan = new Scanner(fRead);
			while(scan.hasNext()) {
				if(un.equals(scan.next()) && pwd.equals(scan.next())) {
					valid = true;}
			}
			fRead.close();
		}catch (Exception e) {
			System.err.println("Err 101: isValid+\n"+e.getMessage());
		}
		return valid;
	}
}

Login.java

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

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

public class Login implements ActionListener {
	JFrame myFrame;
	JTextField txtUsername, txtPassword;
	JLabel lblUsername, lblPassword;
	JButton btnOk, btnCancel;
	JPanel panel;
	
	public Login() {
		myFrame = new JFrame("Login");
		txtPassword = new JTextField("Username", 20);
		txtUsername = new JTextField("Password", 20);
		
		lblUsername = new JLabel("Username");
		lblPassword = new JLabel("Password");
		
		btnOk = new JButton("OK");
		btnCancel = new JButton("Cancel");
		
		panel = new JPanel();
		panel.add(lblUsername);
		panel.add(txtUsername);
		panel.add(lblPassword);
		panel.add(txtPassword);
		panel.add(btnOk);
		panel.add(btnCancel);
		
		btnOk.addActionListener(this);
		btnCancel.addActionListener(this);
		
		myFrame.add(panel);
		myFrame.setVisible(true);
		myFrame.setSize(350, 150);
		myFrame.setLocationRelativeTo(null);
		myFrame.setDefaultCloseOperation(myFrame.EXIT_ON_CLOSE);
	}
	
	public static void main(String[] args) {
		new Login();
	}

	@Override
	public void actionPerformed(ActionEvent e) {
		if(e.getSource().equals(btnOk)) {
			Database db = new Database("Account.txt");
			String user = txtUsername.getText();
			String pass = txtPassword.getText();
			if(db.isValid(user, pass)) {
				JOptionPane.showMessageDialog(myFrame, "Login Successful", "Success", JOptionPane.INFORMATION_MESSAGE);
				myFrame.dispose();
			}else {
				JOptionPane.showMessageDialog(myFrame, "Login Failure", "Failed", JOptionPane.ERROR_MESSAGE);
				//myFrame.dispose();
			}
		}
		else {
			System.exit(0);
		}
	}
}