Java tutorial
import java.awt.event.ContainerEvent; import java.awt.event.ContainerListener; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; public class Main { public static void main(String[] a) { JFrame frame = new JFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JPanel buttonPanel = new JPanel(); buttonPanel.addContainerListener(new ContainerListener() { public void componentAdded(ContainerEvent e) { displayMessage(" added to ", e); } public void componentRemoved(ContainerEvent e) { displayMessage(" removed from ", e); } void displayMessage(String action, ContainerEvent e) { System.out.println(((JButton) e.getChild()).getText() + " was" + action + e.getContainer().getClass().getName()); } }); buttonPanel.add(new JButton("A")); frame.add(buttonPanel); frame.setSize(300, 200); frame.setVisible(true); } }