π Detailed Notes
1. Swing Overview
Swing is a GUI (Graphical User Interface) toolkit for Java. It provides a rich set of components for building desktop applications.
Swing vs AWT:
- Swing components are lightweight (pure Java)
- AWT components are heavyweight (native platform)
- Swing has more components and better customization
- Swing follows MVC architecture
2. Basic Swing Components
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class FirstSwingApp {
public static void main(String[] args) {
// Create frame
JFrame frame = new JFrame("My First Swing App");
frame.setSize(400, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new FlowLayout());
// Create components
JLabel label = new JLabel("Enter your name:");
JTextField textField = new JTextField(20);
JButton button = new JButton("Click Me");
JTextArea textArea = new JTextArea(5, 30);
JCheckBox checkBox = new JCheckBox("I agree");
JRadioButton rb1 = new JRadioButton("Option 1");
JRadioButton rb2 = new JRadioButton("Option 2");
// Add action listener
button.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String name = textField.getText();
textArea.setText("Hello, " + name + "!");
}
});
// Add components to frame
frame.add(label);
frame.add(textField);
frame.add(button);
frame.add(textArea);
frame.add(checkBox);
frame.add(rb1);
frame.add(rb2);
// Display frame
frame.setVisible(true);
}
}
3. Layout Managers
| Layout |
Description |
Use Case |
| FlowLayout |
Components flow left to right, top to bottom |
Simple arrangements |
| BorderLayout |
5 regions: NORTH, SOUTH, EAST, WEST, CENTER |
Main window layout |
| GridLayout |
Equal-sized cells in rows and columns |
Calculator buttons |
| GridBagLayout |
Flexible grid with constraints |
Complex layouts |
4. Event Handling
// Method 1: Implementing Listener Interface
class MyFrame extends JFrame implements ActionListener {
JButton btn;
MyFrame() {
btn = new JButton("Click");
btn.addActionListener(this);
add(btn);
}
public void actionPerformed(ActionEvent e) {
if (e.getSource() == btn) {
JOptionPane.showMessageDialog(this, "Button clicked!");
}
}
}
// Method 2: Anonymous Inner Class
button.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
// Handle event
}
});
// Method 3: Lambda Expression (Java 8+)
button.addActionListener(e -> {
// Handle event
});
5. JDBC (Java Database Connectivity)
JDBC is a Java API for connecting and executing queries with databases.
JDBC Components:
- DriverManager: Manages database drivers
- Connection: Represents connection to database
- Statement: Executes SQL queries
- ResultSet: Stores query results
- SQLException: Handles database errors
6. JDBC Steps
import java.sql.*;
public class JDBCDemo {
public static void main(String[] args) {
// Database credentials
String url = "jdbc:mysql://localhost:3306/mydb";
String user = "root";
String password = "password";
try {
// Step 1: Load the driver
Class.forName("com.mysql.cj.jdbc.Driver");
// Step 2: Establish connection
Connection conn = DriverManager.getConnection(url, user, password);
// Step 3: Create statement
Statement stmt = conn.createStatement();
// Step 4: Execute query (CREATE)
String createSQL = "CREATE TABLE IF NOT EXISTS students " +
"(id INT PRIMARY KEY, name VARCHAR(50), marks DOUBLE)";
stmt.executeUpdate(createSQL);
// Step 4: Execute query (INSERT)
String insertSQL = "INSERT INTO students VALUES (1, 'Ram', 85.5)";
int rows = stmt.executeUpdate(insertSQL);
System.out.println(rows + " row(s) inserted");
// Step 4: Execute query (SELECT)
String selectSQL = "SELECT * FROM students";
ResultSet rs = stmt.executeQuery(selectSQL);
// Step 5: Process results
while (rs.next()) {
int id = rs.getInt("id");
String name = rs.getString("name");
double marks = rs.getDouble("marks");
System.out.println(id + " | " + name + " | " + marks);
}
// Step 6: Close resources
rs.close();
stmt.close();
conn.close();
} catch (ClassNotFoundException e) {
System.out.println("Driver not found: " + e.getMessage());
} catch (SQLException e) {
System.out.println("Database error: " + e.getMessage());
}
}
}
7. PreparedStatement (Recommended)
// Using PreparedStatement (prevents SQL injection)
String sql = "INSERT INTO students VALUES (?, ?, ?)";
PreparedStatement pstmt = conn.prepareStatement(sql);
// Set parameters
pstmt.setInt(1, 2);
pstmt.setString(2, "Sita");
pstmt.setDouble(3, 90.0);
// Execute
pstmt.executeUpdate();
// Reuse with different values
pstmt.setInt(1, 3);
pstmt.setString(2, "Hari");
pstmt.setDouble(3, 78.5);
pstmt.executeUpdate();
pstmt.close();
8. Complete CRUD Example
public class StudentDAO {
private Connection conn;
public StudentDAO() throws SQLException {
String url = "jdbc:mysql://localhost:3306/school";
conn = DriverManager.getConnection(url, "root", "password");
}
// CREATE
public void addStudent(int id, String name, double marks) throws SQLException {
String sql = "INSERT INTO students VALUES (?, ?, ?)";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, id);
pstmt.setString(2, name);
pstmt.setDouble(3, marks);
pstmt.executeUpdate();
pstmt.close();
}
// READ
public void getAllStudents() throws SQLException {
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM students");
while (rs.next()) {
System.out.println(rs.getInt(1) + " - " + rs.getString(2));
}
rs.close();
stmt.close();
}
// UPDATE
public void updateMarks(int id, double newMarks) throws SQLException {
String sql = "UPDATE students SET marks = ? WHERE id = ?";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setDouble(1, newMarks);
pstmt.setInt(2, id);
pstmt.executeUpdate();
pstmt.close();
}
// DELETE
public void deleteStudent(int id) throws SQLException {
String sql = "DELETE FROM students WHERE id = ?";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, id);
pstmt.executeUpdate();
pstmt.close();
}
}