Building UI with Swing

🪟 What is Swing in Java?

Swing is a GUI (Graphical User Interface) toolkit in Java that allows you to create windows, buttons, text boxes, menus, etc., for desktop applications.

It is part of the Java Foundation Classes (JFC) and provides a rich set of components to build modern UIs.

🧱 Swing = GUI Builder for Java

Feature	Description
🧩 Platform Independent	Works on Windows, Mac, Linux—anywhere Java runs
🎨 Customizable	Supports styling and look-and-feel themes
🧠 Event-Driven	Reacts to user actions like button clicks or typing
💡 Lightweight	Built using Java itself (not native OS components)
🧰 Rich Components	Buttons, text fields, labels, tables, trees, etc.

📦 Swing Comes From:

Package: javax.swing
You import it like:
```
import javax.swing.*;
```

🧊 Common Swing Components

Component	Class	Use
Window	`JFrame`	Main application window
Label	`JLabel`	To display text
Button	`JButton`	Clickable button
Text Box	`JTextField`	Input field
Text Area	`JTextArea`	Multi-line text input
Popup	`JOptionPane`	Show messages or alerts
Panel	`JPanel`	Container to group other components

🧠 Example Flow:

Create a JFrame – acts like a window
Add components like JLabel, JButton
Set layout and size
Add event listeners (like button clicks)
Display it using setVisible(true)

🧪 Why Use Swing?

To build desktop apps
Easy to learn and good for beginners
Still used in enterprise/internal tools (even though newer frameworks like JavaFX exist)

✅ Let’s build a simple Form with:

A window (JFrame)
A label (JLabel)
A text field (JTextField)
A button (JButton)
A popup that shows what the user typed

🧑‍💻 Code: `SimpleForm.java`

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

public class SimpleForm {
    public static void main(String[] args) {
        // Create the main frame
        JFrame frame = new JFrame("User Form");

        // Create label
        JLabel label = new JLabel("Enter your name:");
        label.setBounds(50, 30, 150, 30);

        // Create text field
        JTextField textField = new JTextField();
        textField.setBounds(180, 30, 150, 30);

        // Create button
        JButton button = new JButton("Submit");
        button.setBounds(130, 80, 100, 30);

        // Add button action
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String name = textField.getText();
                JOptionPane.showMessageDialog(frame, "Hello, " + name + "!");
            }
        });

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

        // Frame settings
        frame.setSize(400, 200);
        frame.setLayout(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

▶️ How to Run It

Save it as SimpleForm.java
Open terminal in the same folder
Compile:
```
javac SimpleForm.java
```
Run:
```
java SimpleForm
```

🧠 Explanation of the code:

🔧 Basic Setup

JFrame frame = new JFrame("User Form");
➤ Creates the main window titled "User Form".

🏷️ UI Components

JLabel label = new JLabel("Enter your name:");
➤ Displays a label prompting the user to enter their name.
JTextField textField = new JTextField();
➤ A text field where users can type their name.
JButton button = new JButton("Submit");
➤ A button labeled "Submit".

🎯 Positioning

setBounds(x, y, width, height)
➤ Manually positions and sizes each component on the frame.

🖱️ Button Action

button.addActionListener(...)
➤ Adds functionality to the button.
Inside the action:
- textField.getText() gets the entered name.
- JOptionPane.showMessageDialog(...) shows a popup saying "Hello, <name>!".

🖼️ Final Frame Settings

frame.setSize(400, 200); ➤ Sets window size.
frame.setLayout(null); ➤ Uses no layout manager (manual positioning).
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ➤ Closes app on exit.
frame.setVisible(true); ➤ Makes the window visible.