1. As in the AWT, starting point for graphical applications.

2. One of few Swing components that is built on an underlying "heavyweight" window.

3. Main differences in use compared to Frame:

• Components go in the "content pane", not directly in the frame. Changing other properties (layout manager, background color, etc.) also apply to the content pane. Access content pane via getContentPane, or if you want to replace the content pane with your container (e.g. a JPanel), use setContentPane.
• JFrames close automatically when you click on the close button (unlike AWT Frames). However, closing the last JFrame does not result in your program exiting Java. So your "main" JFrame still needs a WindowListener.
• You get Java (Metal) look by default, so you have to explicitly switch if you want native look.

4. JFrame Example: Source Code

JFrameExample.java (Download source code)

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

public class JFrameExample {
  public static void main(String[] args) {
    WindowUtilities.setNativeLookAndFeel();
    JFrame f = new JFrame("This is a test");
    f.setSize(400, 150);
    Container content = f.getContentPane();
    content.setBackground(Color.white);
    content.setLayout(new FlowLayout()); 
    content.add(new JButton("Button 1"));
    content.add(new JButton("Button 2"));
    content.add(new JButton("Button 3"));
    f.addWindowListener(new ExitListener());
    f.setVisible(true);
  }
}

ExitListener.java (Download source code)

import java.awt.*;
import java.awt.event.*;

public class ExitListener extends WindowAdapter {
  public void windowClosing(WindowEvent event) {
    System.exit(0);
  }
}

5. JFrame Example: Result