Java GUI Programming

Introduction to AWT and Swing

AWT (Abstract Window Toolkit) and Swing are Java's libraries for creating graphical user interfaces.

Basic Swing Application

import javax.swing.*;

public class SimpleGUI {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            JFrame frame = new JFrame("Simple Application");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setSize(400, 300);
            
            JLabel label = new JLabel("Hello, Swing!");
            frame.add(label);
            
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
        });
    }
}
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GUI Components

Common components: JFrame, JPanel, JButton, JLabel, JTextField

Component Example

import javax.swing.*;
import java.awt.*;

public class ComponentDemo extends JFrame {
    public ComponentDemo() {
        setTitle("Component Demo");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(400, 300);
        
        JPanel panel = new JPanel();
        panel.add(new JLabel("Name:"));
        panel.add(new JTextField(15));
        panel.add(new JButton("Submit"));
        
        add(panel);
        setLocationRelativeTo(null);
        setVisible(true);
    }
    
    public static void main(String[] args) {
        SwingUtilities.invokeLater(ComponentDemo::new);
    }
}
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Event Handling

Responding to user interactions with event listeners.

ActionListener Example

import javax.swing.*;
import java.awt.event.*;

public class ButtonDemo extends JFrame {
    private JButton button;
    private JLabel label;
    private int count = 0;
    
    public ButtonDemo() {
        setTitle("Button Demo");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(300, 200);
        
        button = new JButton("Click Me!");
        label = new JLabel("Count: 0");
        
        button.addActionListener(e -> {
            count++;
            label.setText("Count: " + count);
        });
        
        setLayout(new FlowLayout());
        add(button);
        add(label);
        
        setLocationRelativeTo(null);
        setVisible(true);
    }
    
    public static void main(String[] args) {
        SwingUtilities.invokeLater(ButtonDemo::new);
    }
}
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Layout Managers

Arranging components in containers.

Layout Example

import javax.swing.*;
import java.awt.*;

public class LayoutDemo extends JFrame {
    public LayoutDemo() {
        setTitle("Layout Demo");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(400, 300);
        
        // Create panels with different layouts
        JPanel mainPanel = new JPanel(new BorderLayout());
        
        JPanel northPanel = new JPanel();
        northPanel.add(new JButton("North"));
        mainPanel.add(northPanel, BorderLayout.NORTH);
        
        JPanel centerPanel = new JPanel(new GridLayout(2, 2));
        centerPanel.add(new JButton("Button 1"));
        centerPanel.add(new JButton("Button 2"));
        centerPanel.add(new JButton("Button 3"));
        centerPanel.add(new JButton("Button 4"));
        mainPanel.add(centerPanel, BorderLayout.CENTER);
        
        add(mainPanel);
        setLocationRelativeTo(null);
        setVisible(true);
    }
    
    public static void main(String[] args) {
        SwingUtilities.invokeLater(LayoutDemo::new);
    }
}
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Creating Forms

Building a registration form with validation.

Registration Form Example

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class RegistrationForm extends JFrame {
    private JTextField nameField, emailField;
    private JPasswordField passwordField;
    private JButton submitButton;
    
    public RegistrationForm() {
        setTitle("Registration Form");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(400, 300);
        setLayout(new GridLayout(4, 2, 10, 10));
        
        add(new JLabel("Name:"));
        nameField = new JTextField();
        add(nameField);
        
        add(new JLabel("Email:"));
        emailField = new JTextField();
        add(emailField);
        
        add(new JLabel("Password:"));
        passwordField = new JPasswordField();
        add(passwordField);
        
        add(new JLabel());
        submitButton = new JButton("Register");
        submitButton.addActionListener(this::handleSubmit);
        add(submitButton);
        
        setLocationRelativeTo(null);
        setVisible(true);
    }
    

    private void handleSubmit(ActionEvent e) {
        String name = nameField.getText().trim();
        String email = emailField.getText().trim();
        String password = new String(passwordField.getPassword());
        
        if (name.isEmpty() || email.isEmpty() || password.isEmpty()) {
            JOptionPane.showMessageDialog(this, 
                "All fields are required!", 
                "Error", JOptionPane.ERROR_MESSAGE);
        } else {
            JOptionPane.showMessageDialog(this, 
                "Registration successful!\nName: " + name, 
                "Success", JOptionPane.INFORMATION_MESSAGE);
        }
    }
    
    public static void main(String[] args) {
        SwingUtilities.invokeLater(RegistrationForm::new);
    }
}
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