import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import javax.swing.*;

public class Login
{
private static JFrame frame;
private static JPanel northPanel;
private static JPanel centerPanel;
private static JPanel southPanel;
private static JLabel headingLabel;
private static JLabel usernameLabel;
private static JLabel passwordLabel;
private static JTextField usernameField;
private static JPasswordField passwordField;
private static JButton loginBtn;

public void start()
{
    try
    {
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
    }
    catch (Exception e)
    {

    }

    new Login().buildLogin();
}

private void buildLogin()
{
    // Build Objects
    frame = new JFrame();
    northPanel = new JPanel();
    centerPanel = new JPanel();
    southPanel = new JPanel();
    headingLabel = new JLabel();
    usernameLabel = new JLabel();
    passwordLabel = new JLabel();
    usernameField = new JTextField();
    passwordField = new JPasswordField();
    loginBtn = new JButton();

    // Labels
    headingLabel.setText("Login");
    headingLabel.setForeground(Color.white);
    headingLabel.setVisible(true);

    usernameLabel.setText("   Username: ");
    usernameLabel.setForeground(Color.blue);
    usernameLabel.setVisible(true);

    passwordLabel.setText("   Password: ");
    passwordLabel.setForeground(Color.blue);
    passwordLabel.setVisible(true);

    // Buttons
    loginBtn.setText("Login");
    loginBtn.setVisible(true);
    loginBtn.addActionListener(new Validate1());

    // Panels
    northPanel.add(headingLabel);
    northPanel.setBackground(Color.blue);
    centerPanel.add(usernameLabel);
    centerPanel.add(usernameField);
    centerPanel.add(passwordLabel);
    centerPanel.add(passwordField);
    centerPanel.setLayout(new GridLayout(2, 2));
    southPanel.add(loginBtn);

    // JFrame
    frame.getContentPane().add(BorderLayout.NORTH, northPanel);
    frame.getContentPane().add(BorderLayout.CENTER, centerPanel);
    frame.getContentPane().add(BorderLayout.SOUTH, southPanel);
    frame.setSize(300, 150);
    frame.setResizable(false);
    frame.setVisible(true);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLocationRelativeTo(null);
}

// Validate1 Class
static class Validate1 implements ActionListener
{
    @SuppressWarnings("deprecation")
    public void actionPerformed(ActionEvent e)
    {
        String username = null;
        String password = null;

        try
        {
            username = usernameField.getText().toUpperCase().trim();
            password = passwordField.getText().toUpperCase().trim();

            if (username.equals("") && password.equals(""))
            {
                usernameLabel.setForeground(Color.red);
                passwordLabel.setForeground(Color.red);
            }
            else
            {
                if (username.equals(""))
                {
                    usernameLabel.setForeground(Color.red);
                    passwordLabel.setForeground(Color.blue);
                }
                else
                {
                    if (password.equals(""))
                    {
                        usernameLabel.setForeground(Color.blue);
                        passwordLabel.setForeground(Color.red);
                    }
                    else
                    {
                        usernameLabel.setForeground(Color.red);
                        passwordLabel.setForeground(Color.red);
                        new Login().validate2(username, password);
                    }
                }
            }
        }
        catch (Exception validateError)
        {
            JOptionPane.showMessageDialog(null, "There was an error Class::Login Class Validate1", "Error", JOptionPane.ERROR_MESSAGE);
        }
    }
}

//Validate2 Method
private void validate2(String getUsername, String getPassword)
{
    String username = null;
    String password = null;

    try
    {
        username = getUsername.toUpperCase();
        password = getPassword.toUpperCase();

        if (username.contains(" ") && password.contains(" "))
        {
            JOptionPane.showMessageDialog(null, "The username and password is invalid", "Error", JOptionPane.ERROR_MESSAGE);
        }
        else
        {
            if (username.contains(" "))
            {
                JOptionPane.showMessageDialog(null, "The username is invalid", "Error", JOptionPane.ERROR_MESSAGE);
            }
            else
            {
                if (password.contains(" "))
                {
                    JOptionPane.showMessageDialog(null, "The password is invalid", "Error", JOptionPane.ERROR_MESSAGE);
                }
                else
                {
                    usernameLabel.setForeground(Color.red);
                    passwordLabel.setForeground(Color.red);
                    System.out.println("All good!!");
                }
            }
        }
    }
    catch(Exception e)
    {
        JOptionPane.showMessageDialog(null, "Error in Class::Login Method:valsidate2","Error", JOptionPane.ERROR_MESSAGE);

    }
}
}

public class Main
{

public static void main(String[] args)
{
    new Login().start();

}

}

import java.io.*;

public class FileData
{

public static void main(String[] args) throws IOException
{
    String file_name = "PATH TO THE TEXT FILE WOULD BE HERE";

    try
    {
        ReadFile file = new ReadFile(file_name);
        String[] aryLines = file.OpenFile();

        for(int i = 0; i < aryLines.length; i++)
        {
            System.out.println(aryLines[i]);
        }
    }
    catch (IOException e)
    {
        //System.out.println(e.getMessage());
        System.out.println("Sorry, dude - no can do!!!n" + e.getMessage());
    }

    try
    {
        WriteFile data = new WriteFile(file_name , true );
        data.writeToFile("This is another line of text");
    }
    catch(IOException e)
    {
        System.out.println("Sorry, dude - no can do!!!n" + e.getMessage());
    }

    System.out.println("Text File Written To");
}

}

import java.io.*;

public class ReadFile
{
private String path;

public ReadFile(String file_path)
{
    path = file_path;
}

public String[] OpenFile() throws IOException
{
    FileReader inFile = new FileReader(path);
    BufferedReader textReader = new BufferedReader(inFile);

    int numOfLines = readLines();
    String[] textData = new String[numOfLines];

    for(int i = 0; i < numOfLines; i++)
    {
        textData[i] = textReader.readLine();
    }

    textReader.close();
    return textData;
}

int readLines() throws IOException
{
    FileReader file_to_read = new FileReader(path);
    BufferedReader bf = new BufferedReader(file_to_read);

    String aLine;
    int numOfLines = 0;

    while((aLine = bf.readLine()) != null)
    {
        numOfLines++;
    }

    bf.close();

    return numOfLines;
}
}

import java.io.*;

public class WriteFile
{
private String path;
private boolean append_to_file = false;

public WriteFile(String file_path)
{
    path = file_path;
}

public WriteFile(String file_path, boolean append_value)
{
    path = file_path;
    append_to_file = append_value;
}

public void writeToFile(String textLine) throws IOException
{
    FileWriter write = new FileWriter(path, append_to_file);
    PrintWriter print_line = new PrintWriter(write);

    print_line.printf("%s" + "%n" , textLine);

    print_line.close();
}
}