Display multiple components in an Internal Frame in Java

At first, set an Internal Frame in the JDesktopPane −

JDesktopPane desktopPane = new JDesktopPane();
JInternalFrame intFrame = new JInternalFrame("Our Frame", true, true, true, true);
desktopPane.add(intFrame);

Now, set the bounds of the Internal Frame −

intFrame.setBounds(50, 90, 200, 250);

Create two components −

JLabel label = new JLabel(intFrame.getTitle(), JLabel.CENTER);
JButton button = new JButton("Demo Button");

Add the two components to the Internal Frame −

intFrame.add(label, BorderLayout.CENTER);
intFrame.add(button, BorderLayout.WEST);

The following is an example to display multiple components in an internal frame −

package my;
import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JDesktopPane;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
import javax.swing.JLabel;
public class SwingDemo {
   public static void main(final String[] args) {
      JFrame frame = new JFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      JDesktopPane desktopPane = new JDesktopPane();
      JInternalFrame intFrame = new JInternalFrame("Our Frame", true, true, true, true);
      desktopPane.add(intFrame);
      intFrame.setBounds(50, 90, 200, 250);
      JLabel label = new JLabel(intFrame.getTitle(), JLabel.CENTER);
      JButton button = new JButton("Demo Button");
      intFrame.add(label, BorderLayout.CENTER);
      intFrame.add(button, BorderLayout.WEST);
      intFrame.setVisible(true);
      frame.add(desktopPane, BorderLayout.CENTER);
      frame.setSize(600, 500);
      frame.setVisible(true);
   }
}

Output

The following is the result after clicking the maximize button on the above displayed Internal Frame −