Account-creation program I just finished a program that is a simple Swing GUI. It takes in user info, such as password and username, turns them into strings, and puts them in a text file called nuserInfo.txt.

I just want corrections on how the code works and what I can do to improve my saving, GUI, and code in general. I'll post all the code below (just one class). Feel free to make any remarks, comments, criticism, or ask any questions in the comments below. 

CreateAccount class:

package passwordProgram;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Arrays;

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

public class CreateAccount implements ActionListener {

    JFrame frame;
    JPanel panel;
    JTextField username;
    JPasswordField password;
    JPasswordField confirmPassword;
    JLabel warningLabel;

    public static void main(String[] args) {
        try {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        } catch (Exception e) {
            e.printStackTrace();
        }
        CreateAccount window = new CreateAccount();
        window.go();
    }

    public void go() {
        frame = new JFrame("Create a new account");
        panel = new JPanel();

        panel.setLayout(new GridBagLayout());

        frame.getContentPane().add(BorderLayout.CENTER, panel);
        panel.setBackground(Color.ORANGE);

        JLabel userLabel = new JLabel("Username:");
        JLabel passwordLabel = new JLabel("Password:");
        JLabel confirmPasswordLabel = new JLabel("Confirm Password:");
        username = new JTextField(15);
        password = new JPasswordField(15);
        confirmPassword = new JPasswordField(15);

        GridBagConstraints right = new GridBagConstraints();
        right.anchor = GridBagConstraints.WEST;
        GridBagConstraints left = new GridBagConstraints();
        left.anchor = GridBagConstraints.EAST;

        right.weightx = (int) 2;
        right.fill = GridBagConstraints.REMAINDER;
        right.gridwidth = GridBagConstraints.REMAINDER;
        // actual GUI

        panel.add(userLabel, left);
        panel.add(username, right);
        panel.add(passwordLabel, left);
        panel.add(password, right);
        panel.add(confirmPasswordLabel, left);
        panel.add(confirmPassword, right);

        frame.setSize(300, 250);
        frame.setVisible(true);

        JButton createAccount = new JButton("Create this account");
        frame.getContentPane().add(BorderLayout.SOUTH, createAccount);
        createAccount.addActionListener(this);

        warningLabel = new JLabel();
        frame.getContentPane().add(BorderLayout.NORTH, warningLabel);
    }


    // This is where the problem is! 
    public void actionPerformed(ActionEvent event) {
        if (!(Arrays.equals(password.getPassword(), confirmPassword.getPassword()))) {
            warningLabel.setText("Your passwords do not match! Please try again.");
        } else if (password.getPassword().length &lt; 1) {
            warningLabel.setText("That password is not long enough! Please try again!");
        } else {
            try {
                FileWriter writer = new FileWriter(new File("nuserInfo.txt"));
                writer.write(username.getText() + "/" + password.toString());
                writer.close();
            } catch (IOException e) {
                e.printStackTrace();
            }        
        }
    }
}
I put your Swing components on the Event Dispatch thread (EDT) in the main method.
I rearranged your Swing component definitions in the go method to group like things together.  I made sure that the JFrame setVisible method was the last method called in the go method.  I added a call to the JFrame setDefaultCloseOperation so that when you closed the GUI, your application would exit.
Your password field returns a character array.  I had to look up how to do it, but you have to convert the character array to a String to write it to a file.
I added the BufferedWriter to your actionPerformed method.


.

package passwordProgram;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Arrays;

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

public class CreateAccount implements ActionListener {

    JFrame          frame;
    JPanel          panel;
    JTextField      username;
    JPasswordField  password;
    JPasswordField  confirmPassword;
    JLabel          warningLabel;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager
                            .getSystemLookAndFeelClassName());
                } catch (Exception e) {
                    e.printStackTrace();
                }
                CreateAccount window = new CreateAccount();
                window.go();
            }
        });
    }

    public void go() {
        panel = new JPanel();
        panel.setLayout(new GridBagLayout());
        panel.setBackground(Color.ORANGE);

        frame = new JFrame("Create a new account");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(BorderLayout.CENTER, panel);

        JLabel userLabel = new JLabel("Username:");
        JLabel passwordLabel = new JLabel("Password:");
        JLabel confirmPasswordLabel = new JLabel("Confirm Password:");
        username = new JTextField(15);
        password = new JPasswordField(15);
        confirmPassword = new JPasswordField(15);

        GridBagConstraints right = new GridBagConstraints();
        right.anchor = GridBagConstraints.WEST;
        GridBagConstraints left = new GridBagConstraints();
        left.anchor = GridBagConstraints.EAST;

        right.weightx = (int) 2;
        right.fill = GridBagConstraints.REMAINDER;
        right.gridwidth = GridBagConstraints.REMAINDER;
        // actual GUI

        panel.add(userLabel, left);
        panel.add(username, right);
        panel.add(passwordLabel, left);
        panel.add(password, right);
        panel.add(confirmPasswordLabel, left);
        panel.add(confirmPassword, right);

        JButton createAccount = new JButton("Create this account");
        frame.getContentPane().add(BorderLayout.SOUTH, createAccount);
        createAccount.addActionListener(this);

        warningLabel = new JLabel();
        frame.getContentPane().add(BorderLayout.NORTH, warningLabel);

        frame.setSize(300, 250);
        frame.setVisible(true);
    }

    // This is where the problem is!
    public void actionPerformed(ActionEvent event) {
        if (!(Arrays.equals(password.getPassword(),
                confirmPassword.getPassword()))) {
            warningLabel
                    .setText("Your passwords do not match! Please try again.");
        } else if (password.getPassword().length &lt; 1) {
            warningLabel
                    .setText("That password is not long enough! Please try again!");
        } else {
            try {
                BufferedWriter writer = new BufferedWriter(new FileWriter(
                        "nuserInfo.txt"));
                writer.write(username.getText() + "/"
                        + new String(password.getPassword()));
                writer.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}