Swing

 Swing is a part of Java's Java Foundation Classes (JFC), which is used to create graphical user interface (GUI) applications. Swing is a lightweight GUI toolkit, meaning it doesn't rely heavily on the underlying system's GUI libraries. Instead, it uses its own rendering engine, making it platform-independent.

Here’s a step-by-step guide to understanding Swing in Java:

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1. Basics of Swing

• Swing is part of the javax.swing package.
• It provides a set of "components" like buttons, text fields, labels, etc.
• Swing follows a Model-View-Controller (MVC) architecture.

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2. Setting Up a Swing Application

Every Swing application typically has:

• A Frame: A main window (like a container).
• Components: Elements like buttons, labels, and text fields.
• Layout Manager: To arrange components.

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3. Common Swing Components

Here are some commonly used Swing components:

• JFrame: The main window.
• JLabel: Displays text or images.
• JButton: A clickable button.
• JTextField: A single-line input field.
• JTextArea: A multi-line text area.
• JCheckBox: A checkbox for boolean selection.
• JRadioButton: Radio buttons for mutually exclusive choices.
• JPanel: A container for grouping components.

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4. Swing Layout Managers

Swing uses layout managers to arrange components:

• FlowLayout: Places components in a row.
• BorderLayout: Divides the container into five areas (NORTH, SOUTH, EAST, WEST, CENTER).
• GridLayout: Arranges components in a grid.
• BoxLayout: Places components in a single row or column.

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5. Writing a Simple Swing Application

Here is an example of a basic Swing program:

import javax.swing.*;  // Import Swing package

public class SwingExample {
    public static void main(String[] args) {
        // Create a JFrame (Main Window)
        JFrame frame = new JFrame("Swing Example");
        frame.setSize(400, 300);  // Set the size of the window
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  // Exit the program when closed

        // Create a JLabel (Text Label)
        JLabel label = new JLabel("Welcome to Swing!");

        // Create a JButton (Button)
        JButton button = new JButton("Click Me");

        // Add components to the frame
        frame.add(label);   // Add the label
        frame.add(button);  // Add the button

        // Set Layout Manager
        frame.setLayout(new FlowLayout());  // Flow layout for components

        // Make the frame visible
        frame.setVisible(true);
    }
}

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6. Adding Event Handling

To make components interactive, we add event listeners. For example:

Adding Action Listener to a Button:

button.addActionListener(e -> {
    System.out.println("Button was clicked!");
});

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7. Key Features of Swing

• Lightweight: Doesn’t depend heavily on native GUI libraries.
• Customizable: Supports Look and Feel (e.g., Metal, Nimbus, etc.).
• Event-Driven: Uses listeners for event handling.
• Pluggable Look and Feel: Can mimic the native look or have a unique style.

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8. Example with Multiple Components

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

public class SwingDemo {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Swing Demo");
        frame.setSize(500, 400);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        // Create a panel
        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(3, 2));  // Grid layout with 3 rows and 2 columns

        // Add components to the panel
        panel.add(new JLabel("Name: "));
        panel.add(new JTextField(10));
        panel.add(new JLabel("Password: "));
        panel.add(new JPasswordField(10));
        panel.add(new JButton("Submit"));

        // Add the panel to the frame
        frame.add(panel);

        frame.setVisible(true);
    }
}